Introduction
This project was completely described in an earlier report dated February 19, 1998.
In the Spring of 1998, the Federal Emergency Management Agency (FEMA) conducted a meeting with representatives of Burnett County, Wisconsin DNR and SEH (Short, Elliott, Hendrickson Inc.) to discuss a flood study of the Yellow River through Burnett County. At this meeting FEMA requested that the project use the NAVD88 vertical datum.
Burnett County has invested heavily in upgrading and maintaining the vertical information in the county. A complete inventory of existing geodetic control was done prior to the final design of the Burnett County Geodetic Control Network (BCGCN).
The level work and adjustments using the NGVD29 datum were described in the first report. A decision was made by Kathy Swingle, Burnett County Surveyor and Land Information Officer, that the county would make the conversion to NAVD88 in support of this upcoming project.
Vertcon adjustments were calculated for all 3rd Order USGS benchmarks. The two large level runs that we had put together in least squares adjustments could be readjusted to NAVD88 by holding benchmarks with know NAVD88 elevations. This is highly preferable over the vertcon transformation.
The Norton STH70 project was recomputed and submitted to NGS as a 2nd order run in support of a problem uncovered with NGS benchmark X46. Hopefully this will be incorporated into the NGS database which will adequately document that project.
This report will cover the readjustment of the other large level adjustment along the Gandy Dancer Trail.
NAVD88 Control For Adjustment
The readjustment of the Norton STH70 work to NAVD88 provided the elevation of station Heidi at the Burnett County Airport at the south end of this project. At the north end of the project, we had ended our work on USGS benchmark TT35B. As previously discussed, this monument was apparently disturbed from it's original position. The Minnesota DOT had run a 2nd Order level run from Hinckley to this monument and Dixon Hoyle, Minnesota NGS Advisor, was able to supply us with both NGVD29 and NAVD88 for this monument which they called TT35B-RESET.
Star*Lev Adjustments
In reprocessing all this data and converting to NAVD88, it became apparent that there was a large change in the two datums between Hinckley and Danbury. In my previous NGVD29 adjustment, I held the MNDOT value, but this was based on a NGVD29 benchmark in Hinckley. I have readjusted the NGVD29 run holding the Vertcon conversion of the NAVD88 value at TT35B-RESET. This revision will yield more consistent results with other benchmarks in Burnett County. The revised results are included at the end of this report and the set of files for this adjustment are included on a diskette named GANDY29C.*. The minimally constrained adjustment is named GANDY29U.*. A chart showing the comparison with published benchmarks for both adjustments is included with this report. It is interesting to note that the minimally constrained adjustment holds Heidi fixed and misses TT35B-RESET by 0.011 feet!! This is phenomenal closure over a very large distance.
For the NAVD88 adjustment, I held Heidi fixed and ran a minimally constrained adjustment. The closure at the various published benchmarks is compared in another chart included with this report. The other benchmarks were converted to NAVD88 using VERTCON for this comparison. The minimally constrained adjustment is named GANDY88U. The closure at TT35B-RESET at the north end of the project is 0.074 feet, which is excellent for distance covered.
In the fully constrained adjustment, Heidi and TT35B-RESET are held fixed and the USGS benchmarks are held partially fixed with an a-priori estimate of standard error assigned of +0.03 feet. The file set for this adjustment is named GANDY88C.*.
Summary
The following pages show the comparison charts discussed above and the final adjusted values for NGVD29 and NAVD88.
The values from the previous adjustment for NGVD29 should be disregarded.
I believe that with the effort that has been made to perform the conversion to NAVD88 by Burnett County, that this new datum should be adopted by the county for future work.
The results of the VERTCON conversion for the USGS, COE and other benchmarks are also included at the end of this report.
Comparison of NGVD29 Adjustment Results Revised 9/29/98
NGVD29 VALUES FROM FINAL CONSTRAINED ADJUSTMENT GANDY29C
T35B-RESET 955.06000
TT34B 950.47454 USGS (Mon. now not found)
TT32B 972.53080 USGS 1946
HEIDI 990.24600
TT31B 1003.76386 USGS 1946 (Mon. now Destroyed)
TT33B 932.66501 USGS (Mon. now Destroyed)
BM437-E 935.69865 PSC Brass Cap on Bridge
WTBMA 1005.55469 Wagner TBM A
WTBMB 1004.05274 Wagner TBM B
CTBMA-1 980.60569
CTBMA-2 957.82302
CTBMA-3 933.08799
TBMJAMISON 933.67280
CTBMA-1-A 1002.97211
CTBMA-1-B 995.24652
CTBMA-1-C 940.91241
TBM28 988.04655
BCBM6 947.25295
BCBM7 932.07565
BCBM8 939.64608
BCBM9 954.73152
BCBM10 931.46336
BCBM11 931.98430
GPSOTTEN 956.00990
TBM23 950.18002
TBM24 951.27782
TBM25 946.36870
TBM26 940.52424
TBM27 957.49345
TBM29 978.66392
GPSOVERLOOKS 975.58180
BCBM189 954.47342
BCBM190 935.59239
BCBM191 957.40413
BCBM192 959.73495
BCBM199 933.38308
BM437-D 933.21111
BM437-C 933.05898
BCBM198 931.33993
BCBM193 981.25736
GPS160 981.38727
GPS181 982.04187
N19TP102 982.65778 BCBM194
N19TP115 976.31311 BCBM195
N19TP128 984.87944 BCBM196
N18TP140 990.98875 BCBM197
GPS141 987.90935
NWWALLNEWDAM 935.02263
ROCK1 934.03518
ROCK2 937.08924
BM437-B(APX) 924.52111
TopNWWING 933.37898
Comparison of NAVD88 Adjustment Results Computed 9/29/98
NAVD88 VALUES FROM FINAL CONSTRAINED ADJUSTMENT GANDY88C
TT35B-RESET 955.17200 MNDOT 2nd Order Value NAVD88
TT34B 950.57505 USGS (Mon. now not found)(VC88)
TT32B 972.62913 USGS 1946 (VC88)
HEIDI 990.32500
TT31B 1003.85601 USGS 1946 (Mon. now Destroyed)(VC88)
TT33B 932.77353 USGS (Mon. now Destroyed)(VC88)
BM437-E 935.79094 PSC Brass Cap on Bridge (VC88)
WTBMA 1005.64681 Wagner TBM A
WTBMB 1004.14517 Wagner TBM B
CTBMA-1 980.69777
CTBMA-2 957.91476
CTBMA-3 933.17930
TBMJAMISON 933.76441
CTBMA-1-A 1003.06448
CTBMA-1-B 995.33883
CTBMA-1-C 941.00463
TBM28 988.13884
BCBM6 947.34524
BCBM7 932.16794
BCBM8 939.73832
BCBM9 954.82326
BCBM10 931.55463
BCBM11 932.07591
GPSOTTEN 956.12064
TBM23 950.28962
TBM24 951.38621
TBM25 946.47420
TBM26 940.62874
TBM27 957.59311
TBM29 978.76209
GPSOVERLOOKS 975.68013
BCBM189 954.58047
BCBM190 935.69615
BCBM191 957.50495
BCBM192 959.83461
BCBM199 933.48763
BM437-D 933.31565
BM437-C 933.16354
BCBM198 931.44445
BCBM193 981.35002
GPS160 981.47453
GPS181 982.12865
N19TP102 982.74261 BCBM194
N19TP115 976.39636 BCBM195
N19TP128 984.96111 BCBM196
N18TP140 991.06896 BCBM197
GPS141 988.00164
NWWALLNEWDAM 935.12681
ROCK1 934.13959
ROCK2 937.19353
BM437-B(APX) 924.62565
TopNWWING 933.48354
