The Accuracy of the Original. GLO Surveys. And Their Relationship to Modern Surveying Technology. Milton Denny, PLS

Transcription

1 The Accuracy of the Original GLO Surveys And Their Relationship to Modern Surveying Technology Milton Denny, PLS

2 66 foot Survey Chain A. Contract Surveyor Given Instructions for their Area of Work B. C. D. E. Given Two Chains - One for work and the other for checking Had to supply their own Compass and Crew Paid at the Rate of Per-Mile when final plat was accepted Work Contracted by Township The Workhorse of the Rectangular Survey System A. A deputy surveyor that was given a contract to survey certain townships was provided two survey chains. one chain was for the work, the second was to be reserved as a check chain. B. In most cases the second chain was also used. Some surveyors tied the handles together in order to increase production. Others would have used the check chain to reference trees. or even to have a second chainins crew. c. The GLo developed a complete set of instructions on how the work was to be carried out. Most surveyors desperate to make a profit, developed short cuts to speed up the work. D. The worse cases of abuse resulted in the surveyor not doing the most basic tasks, such as scribing the trees or setting the required corners.

3 Vernier Gompass 6-inch Needle A. The surveyor was paid twodollars per-mile of Line surveyed B. c. D. E. The accuracy was to be one chain per mile or one foot in eighty feet Most original chains measure four to eight inches longer than 66 ft Most sections measure 30 to 50 feet longer than a mile Other sections may measure shorter than a mile A Gompass Like this Cost a Surveyor About $28 in 1830 A. The 1855 manual states that the accuracy was to be one chain per mile. If a chain is 66 feet and an English mile is 5,280 feet, than the accuracy required was one foot in eighty feet. Not very accurate by today's standards, but remember there was plenty of land available. B. C. Today most full sections of land measure thirty to fifty feet per-mile longer than the original field notes. while in other places the distances may measure shorter that the record measurement. That is why it is important for the surveyor to find as much field evidence as possible. In some early letters of instructions to the field suryeyor, they were told to make sure people received the amount of acreage they purchased. Some surveyors were known to measure one extra chain per-mile to meet this requirement. D. Keeping the compass in working order was a major concern for the surveyor. All compasses have a device known as a needle set. This special device lifts the needle off its pin when the compass is not being used. This keeps the pin from wearing out during travel. 3

4 GLO Township Plat A. All the GLO states have on file township plats, one copy is on file with the state, with the original in Washington, D.C. Copies are available in most states, while more and rnore states have then available on the internet. A surveyor should always consult the plats and field notes before starting to work on a large boundary survey. B. On the plat shown above there are a number of things worth noting. This township would be known as a fractional township. Note the top and west side tears of sections are only partial sections. C. Also, note how sections 24,25 and 36 are larger then normal sections. work in this township would require careful study as to the reason for these deviations from normal size sections. D. One old surveyor told me you should never work more than twenty five miles from home. what he was trying to get across to me was the importance of knowing the area where you are doing you work. 4

5 A. This diagram shows the situation that amodern surveyor is faced with on trying to establish a section corner. B. Almost one hundred per cent of direct evidence of a corners location is now gone. Original posts, tree ties, and tree hacks are long gone. The re-establishment of section corners is now dependent on collateral evidence. C. Collateral evidence is that evidence that would give an indication where the original surveyors had set the corner. D. While using collateral evidence seems simple, the modern surveyor has to weigh one type of evidence against other evidence to determine what is the most creditable location for the corner. E. In many situations the collateral evidence does not agree. The surveyors job is to present the most creditable location of the comer or corners to the client. 5

6 OriginalWitness Tree Set By GLO Surveyor A. For many years after the completion of the original land system, surveyors were able to find the record of original tree scribing. Cutting open the blazed area on a tree promoted faster destruction of the tree. Surveyors would also use other methods, such as boring the tree and counting the tree ring to see if the date of theblaze coresponded with the date of the original survey. B. Surveyors today have one last method of finding the location of the original corner. In some cases it is possible to find the stump holes of the witness trees. If you can verifity that the tree type is the same as called for in the original notes, the tree tie distances and compass direction can be used to locate the original corner. Does not always satisfu the location for the comer. C. Recording the evidence, researching the records, applying modem technology to develop the right comer location, is the art of surveying. 6

7 SteelTape with Spring Batance K e t [INll IrLlT S'lnnl ]\,trh fapits (f, Tt', lrlnr. IrRlrnil: Ailt larrl' RolD lin{rr\ijnil\r) A# -,ihlis}"- Gounting Horces Paces A. Not all distances were measured with a survey chain. The drawing above shows four different methods. B. Top left. The band tape came into general by c. Top right. The steel wire tape was available in 100 ft., 200 ft..,300 ft. length, and in the western states 500 ft. D. Bottom left. The waywiser, used for measuring roads and sometimes land. This waywiser is one half pole or eight and one quarter feet. E. Bottom right. Because of the low pay, surveyors were known to count the paces of their horses for measurement. 7

8 "*li':,1fl';-... ' u-' -.2>i+*".::::;:.::;:;i::. *"*-'-lo.ne. E- Todd, c- lt. t "n22''u-u'" 6dY $--Y't. -< olt- lez "*':xj;;;:-,:;t:s:-:::5-'---,,'ttr- ' L..kt.,at d* p,,r", L' *4rld'Jtl"^r'- 'v'.'.a' 51. r T-,', tt. st Lsrx a...' ^.r-.-r4 C.ft,n F.-,./4t,-r b.-.t..t L\ ''tl' 5214feet 5280 feet sz- / az{ a.trz A. This plat is presented to be able to give you a real world look at the problems encountered in doing a survey, we need to study this plat. B. This survey was done in 1949 by E.E. Todd. He was considered to be one of the better Alabama surveyors. Trying to follow in his footsteps, these are the problems we would encounter. c. He does not tell what kind of evidence he set or found at the corners. This makes it difficult to know if a corner found today is the comer he used. He fails to show any evidence or explain why this section is larger on the south than recorded, and smaller on the west. D. He makes no effort to relate the dimensions to the sections around this parcel. The truth is, many surveyors prior to 1950 did not even provide a survey plat. They just surveyed the lines in the field. E. This survey plat is not an unusual situation. I

9 A. This is a copy of the USGS Quad Sheet. B. This Section one is a closing section in the Northeast corner of the township. c. I used the information provided with the quad map to calculate the sides of the section. Note how different the distances are than on Mr. E.E. Todd's plat. 9

10 Modern Total Station A. This instrument is a modern electronic total station. It measures distances electronically, measures the angles and records the information in a digital format, in a data collector. B. The data collector is returned to the office. where the data is downloaded into a computer. The data is then analyzed and, compared to research records to allow the surveyor to make decisions on the location of the proper placement of the property corners. c- The accuracy of the measurement system of most of these instruments is about 2 millimeters. This woutd be about one quarter of an inch. D. The overall accuracy of a survey performed with this technology may be as high as one foot in fifty thousand feet, compared to one foot in eighty feet for the original surveys. 10

11 Global Positioning System (GPS) A. The technology that is changing how field survey work is performed is the Global Positioning System. This system is able to give accurate measurements over hundreds of square mile areas. B. One important feature of GPS is not needing more than two people to gather the data. A disadvantage, you must have a clear view of the sky to collect data. C. GPS technology is bringing new people into surveying. The physical skills of manual labor is not as important as scientific knowledge and computer skills. D. The accuracy ratio may be as high as one foot in two hundred thousand feet, compared to one foot in eighty feet on the original surveys. E. An important thing to always remember, the professional surveyor still needs to research the records, frnd the field evidence, compare and analyze evidence to provide a good 11

12 A. A tool most surveyors find helpful is the handheld Gps unit. B Most provide an accuracy of ten feet or less if used in conjunction with the WAAS system. This unit provides latitude and longitude. This allows a surveyor to find old survey corners and also find the job site quickly. C. This unit would not be used to survey the land. 12

13 A. Many different digital maps are available to the surveyor. B. The street atlas map as shown above has many uses for surveying. The most common is to quickly locate the job site. These maps can also be used to find out many different types of information important to the professional surveyor. C. We, as surveyors, are starting to see a trend where clients want a digital computer file of the job and do not want a paper map. D. This does present some problems such as having an original signature on the documents. I do believe these issues will be resolved over time. 13

14 Using Your Handheld GPS Wisely Buying the Proper Unit: Make sure the unit will read to one/tenth of a second of latitude or longitude. Make sure the unit has WAAS technology Make sure it is in WGS 84 Make sure the unit has a standard batterv size Additional Software: Street Atlas by Delorme 3-D Topo Quads Helpful Web Sites: wtry.ngs.noaa.eov www. ngs. noaa.sov/qpey'sps.html Milton E. Denny, PLS 3001, Inc the spatiel data compeny P O Box Tuscaloosa, Alabama / cell How GPS Works: htto://electronics,howstufftyorks.com/gps.htm A. Some tips on the purchase of a handheld GPS unit. B. Web sites containing helpful information on the use of GPS. 14

15 Definition of LIDAR Acronym for Llght Detection And Ranging. Airborne Laser System used to acquire X, Y, Z coordinates of terrain and terrain features. A system consisting of a transmitter and receiver that emits modulated laser light and processes the reflections to measure and locate objects and features. 15

16 The complete LIDAR system as installed in the aircraft. 16

17 Airborne Global Positioning System (GPS) Obtained simultaneously with the LIDAR mission. Receivers allow on{he-fly initialization and can reinitialize during flight, Greatly reduces the number of control points required. GPS technology being used in conjunction with the LIDAR technology. 17

18 X, Y and Z data converted to pixels to form an elevation image A digital elevation model of LIDAR data. The elevation difference is color coded to be able to detect differences in elevation. 18

19 rd--,fo'-h l{.14-l*t. ll *l==1eeltr I il ftldy'id!+ Elvis software is developed by the company 3001 Inc. to be able to process LIDAR data. This program was designed to handle more than six million points per square mile. Many different companies can fly LIDAR data. Getting a useful product to the client is the greatest challense. 19

20 Structures and Trees A sample set of raw LIDAR data. This is how the data looks after collection. 20

21 Bare Ground Processed LIDAR, commonly referred to as bare ground. This is the final product most clients are looking forward to getting from the LIDAR provider. 21

22 22 What is the Digital Mapping Camera? The ZII digital camera installed in aircraft.

23 1/[ lnt1ging p0nnercd with [orl Zei:s lo develop o unique lens design nininizing dislortion ond noxirnizing rcsolulion The business end of the camera. Note the eight lens, the inside four collect the black and white. The outside four collect red, blue, green and false color red. 23

24 DMC Components The arrangement of the equipment in the aircraft. 24

25 A person standing on the ground. This image is a three inch pixel. 25

26 A color image using three inch pixel resolution. 26

27 Color tuning of the image using specisl filters. 27

28 3 Inch Ground Resolution An example of the type image that can be developed from this camera. 28

29 DMC - Howdoes it work? 4 overlapping images image mosaicing. apply camera calibration parameters. apply platform calibration E tie point area. tie point check. robust adjustment. projection to virtual perspective. fusion with color composite Technical explanation of the development of the final images. 29

30 Pan-Sharpening Applying the color to the black and white images. 30

31 RGB lmage Data at Original Resolution: GSD - 50cm Pan-sharpened RGB image data: GSD = 12cm Additional pan-sharpening of the data. 31

32 Stadium security photos 32

33 Vegetation Analysis Using the data for environmental purposes, such as vegetation analysis. 33

34 Rapid Response Mapping A key element of this technology is to be able to use it for rapid response for all types of natural disasters. 34

35 Bridge, London H = 500m Scale = 1: 4100 GSD = 5cm July,2003 While the images by the ZII camera are a vast improvement over film cameras. Future irnprovements will bring even better products to the marketplace and will also become more cost effective. 35

36 The End Thank You Milton Dennv 3001, Inc. P O Box Tuscaloosa, AL st mdenny@3001data.com 36