Compare point data with multiple DEMS (independent & isat2?)

[gcperk]

1) Compare i-sat points to TRIM and CEDED for Wetland project (HG) or broader area (?) (Secondary priority)

• extract pts and plot cross crossing. (https://rdrr.io/cran/topoDistance/man/topoProfile.html)

2) Geodetic Points (bcdata catalogue) (GP)

• https://www2.gov.bc.ca/gov/content/data/geographic-data-services/georeferencing/vertical-reference-system
• https://catalogue.data.gov.bc.ca/dataset/mascot-geodetic-control-monuments-high-precision

[gcperk]

Completed some initial exploration comparing TRIM and eDTM to the geodetic points. (Rmd)[https://github.com/bcgov/bc_dtm_testing/blob/main/01_mascot_pt_compare.Rmd].

• eDTM has many points with lower elevation values than geodetic points.
• Some extreme values on coast appear to be difference in edge (eDTM not clipped to coast)
• Geodetic pt many on rock outcrops at sea level
• Error figure for ensemble DTM showing values calculates from geo_pts - eDTM values. Values within 50 m removed for clarity

[HunterGleason]

Hi Gen,

Great initial findings. I know in the states at least the survye buttons are drilled into bedrock if available so they don't move, but I guess could mean they are ~5-10 m above sea level along the coast fairly often then? Almost have a first comaperison betwenn TRIM,CDED and the icesat-2 points done for the wetland area of interest. I was curios what datum you have gone with for the analysis so far? Looks like TRIM uses the 1980 geodetic reference system, not sure if NAD83 or WGS84 is the intended reference ellipsoid? Which one are using for the analysis you have done so far?

Hunter

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Completed some initial exploration comparing TRIM and eDTM to the geodetic points. (Rmd)[https://github.com/bcgov/bc_dtm_testing/blob/main/01_mascot_pt_compare.Rmd].

• eDTM has many points with lower elevation values than geodetic points.
• Some extreme values on coast appear to be difference in edge (eDTM not clipped to coast)
• Geodetic pt many on rock outcrops at sea level

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[HunterGleason]

Here is plot for ICESAT versus CDED constrained to the wetland area of interest. Use a cubic resampling technique to project to BC Albers. Quartiles for residuals are: 0% 25% 50% 75% 100% -102.522217 -18.966064 -11.829590 -4.300476 604.736328

Few but large outliers are present, maybe ICESAT?

And here is for TRIM:

     0%         25%         50%         75%        100% 

-102.543335 -18.990906 -11.831970 -4.277802 604.450195

Very similar but not the same (this is quantiles for TRIM-CDED): 0% 25% 50% 75% 100% -12.80078125 -0.04785156 0.00000000 0.04614258 8.47021484