the calibration of survey equipment
Contents
1. A1 is point A and point B1 is point B LEVEL Hod A1 Hod B1 2 metres 40 metres INSTRUMENT SET UP IN THE MIDDLE THE CORRECT FS TO B1 z FS A1 A B INSTRUMENT SET UP PAST THE END There is no substitute for maintaining equal BSs and FSs when leveling Page 32 of 43 SURVEY EQUIPMENT CALIBRATION APPENDIX D e EXCEL SPREAD SHEET e EDMONTON BASELINE Page 33 of 43 Ratio 10443 221702 2 6185 20104 35651 90967 7906 46770 7531 63219 78048 Diff 2 0 012 0 002 0 003 0 073 0 009 0 008 0 169 0 009 0 133 0 009 0 0349 mm ppm Obs PC 120 2060 453 9665 874 9095 1457 6662 333 7605 754 7095 1337 5680 420 9390 1003 7617 582 6707 Ratio 7757 75253 1070825 19057 62072 175040 7725 83930 7312 111370 162034 SPEC S Part A Part B Computed Values Hor Dist P O 120 210 453 971 874 914 1457 670 333 765 794 713 1337 572 420 943 1003 766 582 675 Sum 0 3893 Means 0 0389 Cor Dist 120 210 453 971 874 914 1457 670 333 765 754 713 1337 572 420 943 1003 766 582 675 Jan 16 DATE 09 PRISM 2 Sip Dist Hor Dist 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 LEICA 405 2541246 EDM 407 BASE LINE CALIBRATION RESULTS Observations HR 0 135 0 137 0 000 0 133 0 135 0 136 0 133 0 133 0 12. adjusting tribrachs Appendix F Checking and adjusting prism antenna poles Appendix E Websites Page 4 of 43 SURVEY EQUIPMENT CALIBRATION blank page Page 5 of 43 SURVEY EQUIPMENT CALIBRATION CALIBRATION OR VALIDATION WHAT DO WE MEAN The terms calibration and validation require some explanation First we need to define calibration in the context of survey equipment Calibration is a comparison between measurements one of known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device The device with the known or assigned correctness is called the standard The second device is the unit under test test instrument or any of several other names for the device being calibrated From the EDM Calibration Manual we have These guidelines describe the four Electronic Distance Measurement EDM calibration baselines in the province of Alberta as well as how to undertake an EDM calibration baseline survey They have been developed to assist users in verifying that their EDM equipment is working within the EDM manufacturer s stated specification for scale error and constant error The guidelines also include requirements for submission of EDM calibration survey data to the Geodetic Control Unit Surveys and Technical Services Section for evaluation Further to the process of simply testing against a known value it is often possible and therefore nece
3. copy in calibration folder In field notes copy in calibration folder In field notes copy in calibration folder In field notes copy in calibration folder Thermometers If possible T In field notes copy in calibration folder In field notes copy in calibration Page 15 of 43 SURVEY EQUIPMENT CALIBRATION MM EDM amp TS Preferably on proper forms Job distances folder and calibration folder Prisms MMM No T amp P Notes or on the EDM forms Job folder and calibration folder Prim poles If possible In field notes copy in calibration MMM No folder MMM No folder Total Stations Yes T In Calibration folder H amp V Angles n a denotes note applicable T denotes temperature P denotes pressure Tribrachs If Possible In field notes copy in calibration The Calibration Label column suggests that a calibration label be applied to each piece of equipment In the case of equipment such rods prism poles and tribrachs etc that may be tested relatively often it would not be practical to maintain the label with dates etc as there simply would not be sufficient space to keep that sort of information on the label It would make more sense to keep a simple log which is available to anyone using the equipment Depending on the size and material of specific calibration labels this may not be practical The importance of recording any adjustments or calibrations cannot be over emphasized Page 16 of 43 SU
4. look like this Measured Corrected Sample Corrected B to A 35 003 34 998 35 003 54 998 BtoC 42 003 41 998 42 005 2 0205 TOTAL C 77 006 76 996 77 006 76 996 4 6 77 001 76 996 77 001 76 996 ERROR 0 005 0 000 0 005 0 000 THEREFORE the error equals B to A B to C A to C The most important thing to remember is that we are testing the EDM PRISM combination We are not testing the ability to setup tribrachs or anything other than the above Page 23 of 43 SURVEY EQUIPMENT CALIBRATION THE KNOWN BASELINE TEST Edmonton The known baseline test is designed to determine both scale and prism offsets in one field operation EDMONTON BASELINE e there are five usable pillars on this baseline e there are a total of ten independent measurements that can be made They Are 937 56 14 to e 937 56 15 e 937 56 16 e 937 56 17 e 937 56 18 937 56 15 to e 937 56 16 e 937 56 17 e 937 56 18 937 56 16 to e 937 56 17 e 937 56 18 937 56 15 to e 937 56 18 You will need e the EDM to be tested e all the prisms that are to be tested e acalibrated thermometer e acalibrated barometer Note that only one prism s can be used to do this test You must measure all the distances with the same prism If more prisms are to be checked this can be accomplished by simply placing each prism in the tribrach at the shortest distance and measuring to it Remember that it is the pris
5. of this paper is the why what and how of a formal calibration policy The definitions of calibration and validation are reviewed The main reasons for a formal calibration policy are discussed which leads into a discussion of what such a policy might look like This paper used the term calibration which in many cases could be exchanged with the term adjustment The paper then discusses the various parts of a mock policy This discussion is followed by a review of how such a policy might be implemented The various pieces of equipment are reviewed as the methods of calibration along with the documentation of the proceedings The focus is on total stations prisms tribrachs and prism antenna poles The paper concludes by reviewing some examples of how to complete a calibration Page 3 of 43 Pages From To 2 3 6 7 8 8 12 12 12 15 15 16 17 18 25 26 29 30 32 33 3 38 39 40 41 42 43 SURVEY EQUIPMENT CALIBRATION TABLE of CONTENTS TOPIC Introduction Abstract Calibration or validation what do we mean Why do we need a formal written calibration policy When do we do an EDM calibration What should a calibration policy include When to calibrate Methods of calibration Documentation of the calibration process APPENDICES Appendix A Calibration Examples Appendix B Baseline Forms Appendix C Daily Check Forms Appendix D EXCEL Spread Sheet Appendix Checking and
6. with a total station the pole should be straight from top to bottom as the pole is rotated e Rolled on a flat surface the entire pole must stay in contact with the surface e Could be checked with plumb bob A bent telescoping pole is not easily straightened this task is best left to a shop that does this kind of work If it is badly bent it should be replaced The normal antenna poles are easier to deal with However once bent the pole is more prone to bending after it has been straightened Checking and adjusting the circular bubble Once it has been determined that the pole is straight the circular bubble can be checked and adjusted if necessary The pole has to be vertical this can be accomplished by using a bracket and a floor point that will ensure that the pole is vertical or any other means that will ensure that the pole is vertical and held in place to allow the adjusting of the circular bubble The bubble is adjusted by forcing the bubble to the center of the circle with the adjustment screws Make sure that the screws are all still snug and that the bubble housing does not move under light pressure Check the pole for length Antenna poles in particular need to be checked for length The pole length is the distance from the tip to the Manufacture s Reference Point MFP on the antenna You will need to consult the user manual for the particular antenna to determine where the MFP is Antenna poles are not automatical
7. 30 0 130 HI 0 238 0 238 0 238 0 238 0 237 0 237 0 237 0 237 0 237 0 237 PRISIM CORRECTION 14 15 15 16 14 16 Page 34 of 43 PPM 16 6 16 6 16 6 16 6 16 5 16 5 13 2 16 6 16 6 16 6 Published DATA Hor LINE Dist ElevB T Elev A CONSTRUCTION THE BASELINE REDUCTION SPREAD SHEET The following is a cell by cell construction of the spread sheet shown above Row 1 blank Row 2 A2 EDM label only C2 input EDM brand Information only D2 input EDM model Information only I2 DATE label only K2 input date Information only N2 SPEC S label only ROW 3 C3 EDM serial number information only N3 Part A label only part a of the specification in mm information only mm label only ROW 4 J4 PRISM prism number Label only K4 input prism number information only O4 b of the specification in ppm information only P4 ppm label only ROW 5 blank ROW 6 A6 BASE LINE CALIBRATION RESULTS label only B7 Published DATA label only G7 Observations label only L7 Computed Values label only ROW 8 A8 LINE label only From to B8 Dist label only Published Horizontal distance C8 ElevA label only Published elevation from point 08 Elev B label only Published elevation to point E8 label only Temperature in degrees C F8 P label only Pressure in mb G8 PPM label only Computed parts per million H
8. 8 HI label only Height of instrument above the plate 18 HR label only Height of reflector above the plate J8 Slp Dist label only Slope distance if that is wnat was measured K8 Hor Dist label only Horizontal distance if that is what was measured L8 Cor Dist label only the measured distance corrected for met readings M8 Hor Dist label only the corrected distance reduced to the horizontal P O label only the Published Distance MINUS the corrected Page 35 of 43 SURVEY EQUIPMENT CALIBRATION OBSERVERED Distance O8 RATIO label only The published distance divided by the difference P8 OBS PC label only the corrected horizontal distance minus PRISM CORRECTION Q8 DIiff2 label only the PUBLISHED distance MINUS the adjusted distance from column P H8 RATIO 2 label only The published distance divided by the second difference ROWS 9 to 18 ONE TIME INPUT ONLY A9 One time Input From to last part of station numbers 937 56 14 14 etc B9 One time Input Published Horizontal distance C9 One time Input Published elevation from point D9 One time Input Published elevation to point FOR EACH OBSERVATION E9 Input Temperature in degrees C F9 Input Pressure in mb G9 FORMULA for specific EDM 2281 8 0 29065 F9 1 0 00366 E9 H9 Input Height of instrument above the plate in metres I9 Input Height of reflector above the plate in metres INPUT ONLY ONE OF THE NEXT TWO COLUMNS the other column MUST be EMPTY J9 If
9. Measured Input Slope distance if that is what was measured K9 If Measured Input Horizontal distance if that is what was measured COMPUTED VALUES L9 FOMRULA IF J9 lt 0 1 G9 1000000 J9 1 G9 1000000 K9 M9 FOMRULA IF J9 gt 0 SQRT L9 L9 C9 H9 D9 19 C9 H9 D9 19 L9 N9 FOMRULA B9 M9 O9 FOMRULA ABS B9 N9 P9 FOMRULA M9 N 22 Q9 JFOMRULA B9 P9 H9 FOMRULA ABS B9 Q9 Enter the formulae into row 9 and pull them down to row 18 ROW 19 M19 SUM label only The sum of all the differences ROW 20 M20 MEAN label only The averages N20 FORMULA average N9 N18 average difference 020 FORMULA average O9 018 average ratio Q20 FORMULA average Q9 Q18 average difference R20 FORMULA average R9 R18 average ratio Page 36 of 43 SURVEY EQUIPMENT CALIBRATION ROW 21 blank ROW 22 M20 MEANS label only The average of all the differences H22 PRISM CORRECTION 14 15 15 16 14 16 label only OBSERVATIONS USED M22 FORMULA M9 M13 M10 PRISM CORRECTION BASED ON THESE OBSERVATIONS It is possible to compute more prism corrections however it is important that distances are not reused Page 37 of 43 SURVEY EQUIPMENT CALIBRATION APPENDIX E CHECKING AND ADJUSTING TRIBRACHS Page 38 of 43 SURVEY EQUIPMENT CALIBRATION CHECKING AND ADJUSTING TRIBRACHS CHECKING TRIBRACHS The errors generated by a tribrach that is out of adjustment will depend on severa
10. RVEY EQUIPMENT CALIBRATION APPENDICES Appendix A Calibration examples Appendix B Baseline forms Appendix C Daily check forms Appendix D Edmonton Baseline EXCEL Spread sheet Appendix E Tribrach checking and adjustment Appendix F Prism Antenna pole checking and adjustment Appendix G Web sites and information sources Page 17 of 43 SURVEY EQUIPMENT CALIBRATION APPENDIX A THREE CALIBRATION EXAMPLES EXAMPLES LEVEL CALIBRATION e TWO PEG TEST EDM CALIBRATION UNKNOWN BASELINE KNOWN BASELINE Page 18 of 43 SURVEY EQUIPMENT CALIBRATION LEVELING ERRORS What errors are we able to detect eliminate or minimize Bubble out of adjustment An out of adjustment bubble causes backsight readings to be either too high or too low while the foresight readings will be the opposite Effect CANNOT be minimized by field methodology Cross hairs out of adjustment e all readings to be either too high or too low e canbe minimized Other Sources e the rod and turning points e applies equally to normal and digital levels remedies are somewhat different DETECTING AND ELIMINATING LEVELING ERRORS CONVENTIONAL amp DIGITAL automatic levels If it is suspected that the main automatic levelling system is out of adjustment the instrument should be adjusted by a professional repair shop By field procedure The normal and best method of minimizing errors in leveling due to instrument misadjustment is to follow
11. Reporting If any piece of measuring equipment is found to be out of calibration this must be reported to the project manager at once If the faulty equipment can be successfully calibrated or adjusted in the field so that is no longer out of calibration the procedure may be performed The incident must still be reported in order that appropriate steps can be taken to ensure that the particular piece of equipment in question can be inspected and cleared for further use At this point we have covered the why and the what We can now move on to the how How do we implement a calibration policy There are several steps to be taken to move from simply having a policy to the actual implementation of the goals set out in the policy Education The first responsibility of the employer is the education of all employees that use measuring equipment manage projects or work with the observations made with the measuring equipment The level of detail will vary from group to group however at the very least all employees must be aware of the calibration policy and have a sound understanding of its goals Without this understanding the goals of the policy cannot be met oimilar to other polices that affect employees upper management must lead the charge One approach that seems to work is to ensure that all those affected by the policy take ownership of the policy or buy into it Training A certain path to failur
12. Serial if applicable Weather Station Thermometer Reading include units User Thermometer Reading include units Thermometer Reading Difference include units EDM Information Form Agency or Surveying Company Contact Name Contact Number ph fax EDM Make EDM Model EDM Serial Number Measurement Units Metres o or Feet o EDM Prism Make Number of Prisms in Set Page 27 of 43 SURVEY EQUIPMENT CALIBRATION CLIENT SRD FILE No 2738 09 08 CREW LD amp DM DATE Jan 16 2009 INSTRUMENT TC 405 SERIAL No 254126 Measure and Record the distances 3 times For slope distances record the HI and HH for each setup WEATHER Clear a indy ing ining HN Check all that apply inst at 937456 14 Temp c 6 Press mb 9325 Hi 0 240 HR 0 410 Le 15 NF NN 16 17 me 18 2028 208 874899 899 946 120 208 453 963 874 899 1437 646 120 209 453 963 874 899 1437 645 120 208 453968 O 874 899 1437 646 Inst at 997456 15 Temp C Press mb 936 Hi 0 240 HR 0 610 Em 16 ae 17 ENE Om 18 333759 759 754 ADD 43374755 475 333 758 754 701 1337 474 333 759 754 701 1337 474 MEM 333 759 754 701 1337 474 inst at937456 16 Temp C Pres m m a 937 56 17 937 56 18 420 936 1003 750 420 936 1003 749 420 935 1003 709 we wu m 937 56 18 8 995638 _ S S o 8 582 865 682865 0 NOTE convert
13. THE CALIBRATION OF SURVEY EQUIPMENT An ancient concept in a modern setting PRESENTED AT THE ALBERTA LAND SURVEYORS ANNUAL GENERAL MEETING BANFF SPRINGS HOTEL APRIL 2012 Prepared by Hugo C Engler A L S Page 1 of 43 SURVEY EQUIPMENT CALIBRATION INTRODUCTION The calibration of survey equipment is not a new issue The concept goes back to the earliest of times when surveyors checked or calibrated their measuring devices against the standard of the day Many active land surveyors will remember the use of the standard tape to calibrate their steel tapes In fact there was a time when obtaining a standard tape was part of the requirements of obtaining one s commission The advent of electronic distance measuring equipment required the establishment and use of baselines to calibrate this type of equipment Later on when global positioning systems became the measuring tools of the day validation base nets were added to the list of calibration tools This brings us to today the second century of our particular organization along with all the great proliferation of total stations GNSS and other instruments used in conjunction with the modern measuring tools Therefore the need for calibration policies and procedures to specifically document a concept that has been part of all surveyors training for as long as surveyors have been around Page 2 of 43 SURVEY EQUIPMENT CALIBRATION ABSTRACT The main theme
14. atteries have enough pin locator at least 60cm charge away Levels Two peg test and adjust Test as required could On larger projects setup be daily a baseline EDM TS Approved baseline OR Overcast days are best Ensure that all the required information is distances Project baseline Prisms Part of baseline test Easiest be done on unknown baseline Prism poles Test for vertical with a total Test bubble in office Adjust bubble as station testing bracket required Tribrachs Test and adjust in office Ensure that all screws test bracket are tight Total stations Check horizontal angles recorded Always double critical and adjust as per the user angles manual NENNEN Check vertical angles and Always double vertical Page 14 of 43 SURVEY EQUIPMENT CALIBRATION adjust as per the user angle on turning manual stations Pipe Locators Test at known location The test location MUST be verified with locator of a different type DOCUMENTATION Every bit as important as the actually testing adjustment and calibration the documentation of the process is the only method of proving that the work was completed Documentation Table In all cases the date and the person s completing the task must be recorded EQUIPMENT SERIAL TEMPERATURE HOW DOCUMENTED Calibration No PRESSURE In field notes copy in calibration folder 0 Cloth tapes If possible Level Rods If Possible In field notes
15. blished DATA LINE APPENDIX C DAILY CHECK FORMS e RTK CHECK e EDM CHECK e TWO PEG TEST Page 30 of 43 SURVEY EQUIPMENT CALIBRATION DAILY RTK BASELINE CHECK FILE DATE PC GPS SYSTEM TOTAL STATION Coord System 37M UTM 10TM J LOCAL DATUM NAD 83 Original NAD 83 CSRS NAD27 ORIGIN of COORDIANTES PRE SURVEY CHECK Check point Published Observed Coordinates Coordinates IN POST SURVEY CHECK Check point TOTAL STATION CHECK Temp C Pressure mb PPM PPM SET Combined Scale Factor used FROM TO PUBLISHED MEASURED Delta Eoo poo SL Lo ee ee Page 31 of 43 SURVEY EQUIPMENT CALIBRATION TWO PEG TEST LEVEL File DATE PC The two peg tests works on the principal that the line of sight through the level is in theory a level plane lt is in fact a very shallow cone with the apex at the instrument When the distances from the instrument to the rod are equal the errors are canceled out therefore giving the true difference in elevation between A and B First setup Rod at A and B GOOD turning points Hod A LEVEL Hod B 20 metres 20 metres With instrument set up past the end all of the error is at ROD B1 The new difference between A amp B contains the error The error is the difference between the two differences To adjust the level it is forced to read the correct reading at B1 on the second setup by adjusting the line of sight Second Setup Point
16. determine whether or not that particular piece of equipment is providing the correct results This procedure does not go into detail as to the actual performance of any test or calibration It simply outlines the general method or procedure to be used The owners manuals are a good source of information to assist in testing adjusting or calibration Whenever one piece of equipment is tested against another it is paramount that the second piece has been calibrated tested and or adjusted and therefore is the standard The following table outlines the basic methods and conditions for performing calibrations testing or adjustments Methods Table EQUIPMENT TESTED AGAINST CONDITIONS COMMENTS oteel tapes Approved standard tape Both tapes to be at the Use tension handles same temperature and fully supported Cloth tapes Any tested steel tape Correct steel tape for Use tension handles Page 13 of 43 SURVEY EQUIPMENT CALIBRATION ewm 0 Level rods Any tested steel tape Correct steel tape for temperature if rod face is metal Rod Bubbles Known vertical Ensure testing item is in fact vertical Thermometer A thermometer known to be Allow enough time for correct the thermometers to acclimatize Barometers A barometer known to be If done at an airport correct ensure that it is the ABSOLUTE pressure you are given Pin Locators Test at a known iron post Known post should be Ensure that the before use counter sunk or keep b
17. e is to simply develop and present a policy and expect it to be accepted whole heartedly without proper education and training The extent of the training portion of implementation will depend on the number of people involved In larger organizations it is vital to train more than one person to perform any one function The process of performing calibrations and testing will involve project managers as well as field Staff It may not be necessary that each crew chief is fully trained in the process but it is Page 11 of 43 SURVEY EQUIPMENT CALIBRATION necessary that all project manages and crew chiefs are fully conversant with the policy and how itis to be implemented Each office should have at least one person who is fully trained to manage the policy and actually perform equipment calibrations This includes e Determining whether or not a piece of equipment requires testing or calibration e Performing the actual calibration testing process e Recording the results e Filing or directing the filing of the results e Maintaining an overall calibration log A certain number of field personnel must also be trained to complete the required field observations for all types of calibration and testing as well as to perform basic calibrations in full WHEN to CALIBRATE The timing of the calibration or testing of equipment is dependent on a number of factors and can therefore not be prescribed in a rigid manner This procedure ou
18. e procedure as calibration Gone are the days when most everything was done without a lot of paperwork Nowadays everything has to be documented This requirement affects us in all walks of life f it is not written down it never happened First and foremost from the Surveys Act we have Standard of measure 11 1 The measure of length used in surveys made under this Act must be the Canadian or the International System measure of length defined by the Weights and Measures Act Canada 2 A surveyor shall verify a all tapes used by the surveyor by comparison with a subsidiary standard of a type approved for that purpose by the Director or by a person authorized in writing by the Director and b all electronic linear measuring devices used by the surveyor by comparison with calibration base lines established by the Minister for that purpose The practice review board is of the opinion that in order to remain competent within the context of the modern geomatics environment it is necessary to develop and implement such a policy as well as the regular checking and calibration of all surveying equipment and auxiliary equipment such as thermometers and barometers Then we have other considerations Many of our clients large long term construction site projects in particular require documentation of a calibration policy If there is ever a question as to measurements in particular when there is some disagreement the mere fact that
19. for this policy to function certain responsibilities are assigned to both the employer and the employees The employer is responsible e For the education of the employees with respect to this policy e ensure that selected employees are properly trained to perform equipment calibrations and are capable of assessing the results e ensure that the employees have the means to implement this policy e o provide all the necessary forms etc e ensure that the policy is observed e determine how and when equipment is to be calibrated e determine whether the calibration is done in house by the vendor or a professional equipment repair and calibration shop e Maintain a record of all calibrations performed Project managers are responsible e To ensure all measuring equipment used on a particular project falls within the scope of this policy e o ensure that staff are aware of the policy e ensure that staff have been properly trained to detect when equipment might be out of calibration and how to deal with the problem The employees are responsible e he actual implementation of the policy e Ensuring that equipment is functioning properly Page 9 of 43 SURVEY EQUIPMENT CALIBRATION e hat whenever a piece of equipment has been subjected to an incident that would dictate that a new calibration be completed that such a calibration is performed e The recording of the results e To inform the pro
20. ject manager of any defective equipment and ensure that that piece of equipment is labeled as OUT of CALIBRATION and is taken out of service until such time as it is performing properly e consult with the employer or project manager as to how to proceed when in doubt Procedures Whenever a piece of equipment is to be calibrated the following steps must be in place e he person s performing the calibration must be well acquainted with the specific procedure for that particular piece of equipment e The equipment owner s manual if any has been reviewed with respect to the procedure e is a company procedure in place that this procedure is reviewed and fully understood e All the proper forms must be in hand When to calibrate There are many reasons why a piece of equipment should be calibrated Some of those reasons are e Statutory as per the Surveys Act or other relevant legislation e Event driven such as o Damaged equipment o New equipment o Rental equipment e Time driven such as o Heavily used o Unused for an extensive period of time o Prescribed calibration schedules Page 10 of 43 SURVEY EQUIPMENT CALIBRATION Record keeping The simple fact that a piece of equipment was calibrated is in itself a good start however unless this fact is recorded and filed in the proper format the process becomes exercise in futility All calibration work shall be recorded in the prescribed manner
21. l factors e If only the bubble is out of adjustment e If only the plummet is out of adjustment gt If both are out of adjustment These errors are basically unpredictable and impossible to correct for The one thing that is known is that the total station prism is not setup over the point thereby creating an error in distances as well as angles The only solution is the make sure that the tribrach is checked and properly adjusted Checking tribrachs is a very important undertaking The process consists of two main steps e Checking and adjusting the circular bubble e Checking and adjusting the optical plummet Checking and adjusting the circular bubble The purpose of the process is to ensure that when the circular bubble is centered in the circle the tribrach is in fact level In order to check the circular bubble one needs a method of ensuring that the tribrach is in fact level One can use a number of methods to achieve this among them are e Use a target equipped with a good tubular bubble complete with marking e The electronic collimation in a modern total station e Any other means that utilizes a bubble that is superior to the circular bubble Once the tribrach is known to be level the circular bubble is adjusted by forcing the bubble to the centre of the circle by adjusting the screws that exist for that purpose Ensure that the bubble is still firmly controlled by these screws Checking and adjusting the optical plum
22. ly interchangeable even within a single manufacturer The length of a prism pole is the distance from the tip to the centre of the prism or the target depending on the type of prism Many prism poles have a graduated scale do not assume that the scale reading will give you the correct prism height As with antenna poles prism poles are not automatically interchangeable with the many prism types available Measure the length Page 41 of 43 SURVEY EQUIPMENT CALIBRATION APPENDIX G WEB SITES e EDM Calibration Manual e Calgary GPS Validation manual e Edmonton GPS Validation manual e EMAIL for 2012 Calibration Presentation Page 42 of 43 SURVEY EQUIPMENT CALIBRATION WEB SITES This EDM Calibration manual can be found at http www srd alberta ca LandsForests DirectorOfSurveys document S EDM Calibration BL Manual pdf URL for Calgary GPS Validation manual http www srd alberta ca LandsForests DirectorOfSurveys document s CalgaryGPSValidationNetworkManual Mar 1997 pdf URL for Edmonton GPS Validation manual http www srd alberta ca LandsForests DirectorOfSurveys documents Edm ontonGPSValidationNetworkManual Mar 1997 pdf EMAIL for this paper the 2012 ALSA AGM Calibration presentation englerh mmm ca subject line AGM Presentation Page 43 of 43
23. m EDM combination that is being tested For the best results prisms should be matched to a particular total station unless all prisms in use are of the same make and model and configured in the same way Page 24 of 43 SURVEY EQUIPMENT CALIBRATION Measure and record all distances At each setup measure the e temperature e pressure the instrument height e the reflector height If you measure the e SLOPE DISTANCES you will need amp HT measurements e HORIZONTAL DISTANCES you will not need the HI and HT Record all observations on the proper form s If you are using the EXCEL spread sheet to do the reductions see appendix B for the sample completed observation and reduction forms you will need to create the spread sheet Page 25 of 43 SURVEY EQUIPMENT CALIBRATION APPENDIX B BASE LINE FORMS BAROMETER INFORMATION e THERMOMETER INFORMATION e EDM INFORMATION e OBSERVATION FORM FOR EDMONTON e EXCEL REDUCTION FORM Page 26 of 43 SURVEY EQUIPMENT CALIBRATION FROM ASRD BASELINE MANUAL Barometer and Thermometer Calibration Form Date Location of Known Standard Weather Station Observer BAROMETER CALIBRATION User Barometer Make User Barometer Model Serial if applicable Weather Station Barometer Reading include units User Barometer Pressure Reading include units Pressure Reading Difference include units THERMOMETER CALIBRATION User Thermometer Make User Thermometer Model
24. met The purpose of this process is to ensure that when the tribrach is in fact level the optical plummet is aimed exactly at a point that is known to be precisely under the centre of the tribrach The tribrach should be forced centre mounted on a bracket firmly fixed to a wall A target on the floor must be set by a suitable method that will ensure that the target is precisely under the centre of the tribrach With the tribrach level and centred over the target the optical plummet cross hairs are forced to point at the target by using the adjustment screws in the tribrach You will now have a tribrach that will when leveled in fact be directly over the point within the manufacture s specifications This is usually in the order of 1mm per metre above the ground Page 39 of 43 SURVEY EQUIPMENT CALIBRATION APPENDIX F CHECKING AND ADJUSTING PRISM ANTENNA POLES Page 40 of 43 SURVEY EQUIPMENT CALIBRATION CHECKING AND ADJUSTING PRISM ANTENNA POLES CHECKING PRISM ANTENNA POLES Prism antenna poles can have the following issues e The pole is not straight e The circular bubble is out of adjustment e he pole is not the correct length The first two issues will generate random and unpredictable errors while the third will generate a constant error that if detected soon enough could be compensated for Checking and correcting pole straightness The straightness of the pole can be checked in several ways e Check
25. mm to mb mm 1 33333 2 mb 741 68 mm 1 333333 988 9 mb To convert inches to mb in 33 866666 mb 29 2 33 86666 988 9 mb Page 28 of 43 Ratio 10443 221702 2 6185 20104 35651 90967 7906 46770 7531 63219 78048 Diff 2 0 012 0 002 0 003 0 073 0 009 0 008 0 169 0 009 0 133 0 009 0 0349 mm ppm Obs PC 120 2060 453 9665 874 9095 1457 6662 333 7605 754 7095 1337 5680 420 9390 1003 7617 582 6707 Ratio 7757 75253 001 5 19057 62072 175040 7725 83930 7312 111370 162034 SPEC S Part A Part B Computed Values Hor Dist P O 120 210 453 971 874 914 1457 670 333 765 794 713 1337 572 420 943 1003 766 582 675 Sum 0 3893 Means 0 0389 Cor Dist 120 210 453 971 874 914 1457 670 333 765 754 713 1337 572 420 943 1003 766 582 675 Jan 16 DATE 9 PRISM 2 Sip Dist Hor Dist 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 0 000 EDM BASE LINE CALIBRATION RESULTS Observations HR 0 135 0 137 0 000 0 133 0 135 0 136 0 133 0 133 0 130 0 130 HI 0 238 0 238 0 238 0 238 0 237 0 237 0 237 0 237 0 237 0 237 PRISIM CORRECTION 14 15 15 16 14 16 Page 29 of 43 PPM 16 6 16 6 16 6 16 6 16 5 16 5 13 2 16 6 16 6 16 6 Pu
26. n The term is similar to the term legislation or an Act Procedure Procedure is a prescribed set of instructions or steps to be taken to achieve the goals of a policy The term is similar to regulations pursuant to a piece of legislation If policy can be described as the what procedure would be the how to What should a calibration policy include A calibration policy should outline objectives of the organization in the context of calibration of surveying equipment The following is a sample outline of such a policy Policy Statement This organization wishes ensure that all surveying equipment and auxiliary measuring equipment are maintained in such so that all measurements made using owned or rented equipment are accurate and reliable To that end we are committed to the equipment calibration policy and the implementation of the policy and its procedures Page 8 of 43 SURVEY EQUIPMENT CALIBRATION Scope The requirements set out in this policy shall apply to all tools and equipment used to make measurements whether these measurements are distances lengths angles temperature or pressure Furthermore this policy shall apply to all measuring equipment used on any project irrespective of the ownership of that equipment Equipment that does not perform to specifications or is prone to go out of adjustment shall be taken out of service This must then be brought to the attention of the employer Responsibilities In order
27. nce in reading then the second setup should be repeated in full SECOND SETUP FINAL READINGS Fsa1 FSBt DIFF AT Bi CORR FS B1 ss 096 _ Page 21 of 43 SURVEY EQUIPMENT CALIBRATION UNKNOWN BASELINE CHECK Another method of checking the total station prism combination is the so called unknown base line check It is a simple procedure that requires 3 tripods and tribrachs and one prism Set the three tripods up in a line lined up by eye is good at a spacing of 30 to 50 metres they do not need to be setup over anything The tripods or tribrachs are NOT TO BE MOVED during the procedure Tripod A Tripod B Tripod C 30 40m 30 40m 1 Place the instrument in the tribrach at B Measure B to A and B to C horizontal distance 2 Place instrument in the tribrach at A Measure horizontal distance A to C Any error is contained in each measurement B to A B to C and A to C therefore the sum of B to A B to C contains the error twice while A to C contains the error only once USE ONLY ONE PRISM PER CHECK DO NOT MOVE TRIPODS or TRIBRACHS SET UP 1 Instrument at B Move the prism from A to C A B SET UP 1 Instrument at A A B Page 22 of 43 SURVEY EQUIPMENT CALIBRATION Instrument at B e Measure B to A e Move the prism to C e measure B to C Instrument at e measure A to C The table should
28. ssary to make adjustments to the equipment to bring it back into calibration For the purposes of this discussion the terms calibration and adjustment may both be used to describe the process of bringing a piece of equipment into specifications The validation process differs significantly from calibration Validation goes beyond simple calibration The validation process includes the following e he equipment o Is it capable of achieving the required accuracy under project conditions o Arethe resulting measurements within specifications that is is it properly calibrated e he procedures used in the field as well as in the office e n some cases even the personnel become part of the process From the Edmonton GPS Validation manual we have The validation networks may also be used to evaluate proposals from GPS survey contractors A validation survey on a GPS basenet may be required to assess the proposed GPS positioning system and determine with confidence whether it can meet contract accuracy requirements A positioning system in this context includes the equipment and procedures used for data collection as well as the software and procedures used for the data processing and adjustment Page 6 of 43 SURVEY EQUIPMENT CALIBRATION Why do we need a formal written calibration policy Why do we need a written policy on equipment calibration Is this not something that we do in our day to day operations without actually documenting th
29. test the following is required e The level to be tested e Agoodrod e Atape 20 mor longer e A good tripod e Two iron bars or something else suitable for setting two temporary bench marks or turning points Set the two turning points approximately 40 metres apart The ground should be level and solid There must be a suitable setup point in the middle and approximately 2m past one end of the line between the points Set a lath or other suitable marker at the midpoint between the turning points using the tape You must be able to read the rod clearly from 2 m past the end of the line to the far rod or move the instrument further away until you can clearly read the rod Adjust the baseline to suit your particular level STEP 1 Level in the middle Read and record both the A rod and the B rod The difference between the readings is the true difference in elevation between A and B FIRST SETUP Instrument in the middle Page 20 of 43 SURVEY EQUIPMENT CALIBRATION Set up level at the end FSBt DIFF A1 B1 CORR FS B1 1575 1929 0 354 0 003 Now adjust the cross hairs to read the correct reading of 1 962 at B Re read the road at A there should not be a significant difference from the initial reading at A Assuming 40 m between rods we have 0 003 40 20 0001m per metre or a maximum of 0 0002 difference in the reading at rod A If there is a significant differe
30. the time tested practice of keeping backs sights as close to equal as practical This procedure should be followed for each individual set up as well as the total back sights and fore sites between bench marks This procedure is much simplified with the advent of digital levels that also read the distance to the rod CHECK CIRCULAR BUBBLE The adjustment of the circular bubble is a two step process First centre the bubble in the circle e turn the level 180 e bring the bubble one half of the way back to the centre of the circle using the bubble adjustment screws e bring the bubble to the centre of the circle repeat these steps until the bubble stays well within the circle at all times MISS ALIGNMENT of the CROSS HAIRS The detection of the miss alignment of the crosshairs is accomplished and corrected by the two peg test The two peg test works on the theory that if the distance from the level to the rods is the same then the error due to any cross hair miss alignment will be equal and therefore eliminated Page 19 of 43 SURVEY EQUIPMENT CALIBRATION THE TWO PEG TEST The two peg tests works on the principal that the line of sight through the level is in theory a level plane It is in fact a very shallow cone with the apex at the instrument When the distances from the instrument to the rod are equal the errors are canceled out therefore giving the true difference in elevation between A and B In order to complete a two peg
31. there is a policy in place may well quell any further questions regarding equipment If you can also show that you are adhering to this policy there should not be any further doubts It just makes sense to have a policy that staff can refer to when the question of calibration comes up Page 7 of 3 SURVEY EQUIPMENT CALIBRATION WHEN TO DO AN EDM CALIBRATION When to calibrate will come up later however since when may be as important as why we can look at it now as well as later From the EDM Calibration BL Manual we have In general there are three situations under which a Land Surveyor or other users of EDM equipment conduct EDM calibration surveys 1 As arequirement for an Alberta Survey Control project for the establishment and or maintenance of Alberta Survey Control Markers ASCMs 2 Statutory requirement under Part 1 Section 11 2 b of the Surveys Act which requires an Alberta Land Surveyor to verity all electronic linear measuring devices used by him by comparison with calibration base lines established by the Minister for that purpose 3 Check the quality of the EDM in situations where it has been damaged during regular surveying operations or when the EDM is old and may no longer be operating within the manufacturer s specifications Policy versus procedure At this point let us look at the terms policy and procedure in this setting Policy Policy is plan of action adopted by an individual or organizatio
32. tlines events that will lead to some form of testing to ensure correct readings are obtained as well as provide timing guidelines Events that could lead to testing Events that could lead to testing include e Equipment is damaged e Equipment has been subjected to shock e Equipment has been repaired e Rental equipment e New equipment e significant change in weather or elevation since its last test or use e The recommended time limit for a specific piece of equipment has expired e Achange in the combination of total station EDM and reflectors Page 12 of 43 SURVEY EQUIPMENT CALIBRATION Hecommended timing of calibration assuming none of the above events would dictate an additional test e Steel tapes annually and prior to an official survey e EDM and total stations annually or when required for an official survey e Reflectors annually e Barometers annually or when move to a significantly different elevation e Thermometers annually e Tribacs quarterly bubble and centering device gt Reflector antenna poles and bubbles at least weekly bubble verticality and straightness e Levels before each project and as often as required during a project to ensure its proper adjustment e leveling rods and rod bubbles at the start a project and in conjunction with the level METHODS of CALIBRATION Each piece of survey equipment has its own unique requirements and must be tested in a manner designed to
Download Pdf Manuals
Related Search