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Detail surveying with network-RTK - an accuracy research

Detail surveying with network-RTK - an accuracy research. Diploma thesis: Robert Odolinski & Johan Sunna. 2009-04-24, Robert Odolinski & Johan Sunna. Background and objectives. Background material: - proposed control methods for detail surveying with network RTK

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Detail surveying with network-RTK - an accuracy research

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  1. Detail surveying with network-RTK- an accuracy research Diploma thesis: Robert Odolinski & Johan Sunna 2009-04-24, Robert Odolinski & Johan Sunna

  2. Background and objectives • Background material: - proposed control methods for detail surveying with network RTK - theoretical assumptions of the expected accuracy levels • Objectives: - estimate if the control methods are practically useful - can the theoretical assumptions of accuracy levels be adjusted to standardised tolerances for such control methods?

  3. Control method:”Revisit with network RTK” • The control method refers to horizontal and vertical level • New fixed ambiguity solution between each control point • At least 20 minutes between each new surveying loop (and revisit) • Surveying in the morning and in the afternoon for some revisits

  4. Control method:”Separate control with conventional technique” • The detail points were measured with a total station (free stationing) in a local system • The measured detail points were then compared to the network RTK points

  5. Proposed accuracy levels The following accuracy levels are within a confidence level of at least 95% based on estimated standard errors: • Revisit network RTK – integrated with the production measurements or processed alone: -horizontal deviation  55 mm -deviation in height  100 mm • Control with total station of point originally measured with network RTK: -unitary transformation: unit-weight standard error (per coordinate)  15 mm -translation in height: standard deviation  35 mm -deviation in distance  40 mm -deviation in height difference  100 mm -deviation in height (after estimating a shift)  70 mm

  6. Surveying areas (4 areas)- Teknikparken, Bomhus and Stigslund

  7. Results from area 1-3(Teknikparken and Bomhus)- modification of the proposed accuracy levels

  8. Separate study of the centering standard error- concerning the prism pole for the total station The centering standard error was estimated to approximately 14 mm

  9. Proposal of new accuracy levels- based on area 1-3 and assumptions • Prerequisites: The new accuracy levels are within a confidence level of at least 95% based on estimated standard errors. The estimated standard errors are in addition based on results from area 1-3 and from the following assumptions: • horizontal standard error for the total station of 5 mm • centering standard error for the rover pole of network RTK of 14 mm • tripod used for the prism pole for the total station  centering standard error = 0 mm

  10. Proposal of new accuracy levels, cont.- based on area 1-3 and assumptions(note that parenthesis = the old proposed accuracy levels) • Revisit network RTK – integrated with the production measurements or processed alone: -horizontal deviation  60 mm (55 mm) -deviation in height  60 mm (100 mm) • Control with total station of point originally measured with network RTK: -unitary transformation: unit-weight standard error (per coordinate)  20 mm (15 mm) -deviation in distance  45 mm (40 mm) -translation in height:standard deviation  20 mm (35 mm) -deviation in height difference  50 mm (100 mm) -deviation in height (after estimating a shift)  40 mm (70 mm)

  11. Results from area 4(Stigslund)- independent test of the new accuracy levels

  12. Results from area 4, cont.(Stigslund) - independent test of the new accuracy levels

  13. Discussion • We consider that the control method ”revisit with network RTK” is practically useful and efficient, because of the integration possibilities with the production measurements. • Separate control with conventional technique (total station/leveling instrument) is not practically useful to integrate with the production measurements, however it is more useful when ordered by e.g. a contractor. • The centering standard errors have more influence of the horizontal control than we expected. • This study achieved a horizontal standard error of 10 mm and standard error in height of 15 mm, which is comparable with similar studies carried out lately (e.g. Edwards et al. 2008). To achieve the horizontal accuracy, a tripod of some kind is necessary to minimize the influence from the centering errors.

  14. Discussion, cont. • It is important to mention that this is an accuracy research in Gävle (autumn 2008), and it should not be considered as a standard for control of detail surveying with network RTK. The conditions in this study are considered to be very favorable. • The accuracy of network RTK can be influenced by e.g.: - solar cycle sunspot (maximum in year 2011) - distance to reference stations (SWEPOS) - location inside our outside the SWEPOS-network (the coast) - the geoid model (SWEN05 was used, now SWEN08 is available) - the antenna phase center - etc… • The accuracy levels can in the future be adjusted to standardized tolerances, but more studies at different locations and under other conditions are then necessary.

  15. The study is available at Lantmäteriets homepage as a report: LMV-Rapport 2009:2 Rapportserie: Geodesi och Geografiska informationssystem. • Thanks for listening! Robert Odolinski robert.odolinski@lm.se Johan Sunna johan.sunna@lm.se

  16. Equipment Total station: Trimble 5601 DR 200+ GNSS receiver: Topcon HiPer+ The GNSS receiver has been configured based on recommendations of ”Kortmanual för mätning med SWEPOS Nätverks RTK tjänst”, with the following parameters: • Elevation cut-off angle 15 • Mean values of 5 observations, with at least one second between each observation • Max antenna height 2 m • Max PDOP 3

  17. Proposed accuracy levels - calculations Estimated standard errors: s0;point are given by a priori standard error horizontal = 15 mm where the estimated standard error are scaled by F-distribution at a risk level of 5% with the following approximation equation: s0;point horizontal(0.96 + ö-0.4) horizontal(0.96 + (2n-3)-0.4) and n = 20, where -3 are given by unitary transformation (3 parameters) which gives: s0;point  20 mm  s0;coord  20/2  15 mm shdiff are given by a priori standard error height = 25 mm where the estimated standard error are scaled by F-distribution at a risk level of 5% with the following approximation equation: shdiffheight (0.96 + ö-0.4) height (0.96 + (n-1)-0.4) and n = 20 gives: shdiff 35 mm

  18. Proposed accuracy levels - calculations The following accuracy levels are within a confidence level of at least 95% based on estimated standard errors: Revisit network RTK – integrated with the production measurements or processed alone: -horizontal deviation  55 mm 2·2·Max(s0;point) =2,6·position -deviation in height  100 mm 2·2·Max(shdiff) = 2,8·h Control with total station of point originally measured with network RTK: -unitary transformation: unit-weight standard error (per coordinate)  15 mm s0;koord -translation in height: standard deviation  35 mm shdiff -deviation in distance  40 mm 2·Max(s0;point) = 2,7distance -deviation in height difference  100 mm 2·2·Max(shdiff) = 2,8h -deviation in height (after estimating a shift)  70 mm 2·Max(shdiff) = 2,8height

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