Hello all,
I want to get the error for each GCP before warping so I can calculate the RMSE
before georeferencing.
With a list of GCPs, is it possible to get the eventual map location of each
pixel coordinate to calculate the transformation error for each GCP?
I have tried to use GCPsToGeoTransform but that gave me a map location that was
further from the intended chosen GCP coordinate than the actual post-
georeferencing pixel location.
Here is my GCPsToGeoTransform code:
##CODE_START
from osgeo import gdal
#list of GCPs
gcpjson={'0': {'row': 5305.626973704321, 'col': 1158.432032601927, 'lat':
-107.18221364936802, 'lon': 35.08107313264506}, '1': {'row': 778.3230540174817,
'col': 2317.0737231100225, 'lat': -107.17634116783263, 'lon':
35.09958594602314}, '2': {'row': 3950.8777704175645, 'col': 4880.465723118029,
'lat': -107.163460244414, 'lon': 35.08679518563491}, '3': {'row':
7609.882307742781, 'col': 4407.027704042081, 'lat': -107.16570574683065, 'lon':
35.07164256912238}, '4': {'row': 1822.0904204049455, 'col': 6486.900377637105,
'lat': -107.15529960157271, 'lon': 35.096105471961536}, '5': {'row':
6291.396402113635, 'col': 7216.1033738731185, 'lat': -107.15180240538085,
'lon': 35.077317337370516}}
#New list to put in gdal.GCP objects into
gcpList=[]
#Load GCP objects into gcpList
for gcp in gcpjson:
gcpList.append(gdal.GCP(gcpjson[gcp]['lat'],gcpjson[gcp]['lon'],0,gcpjson[gcp]['col'],gcpjson[gcp]['row']))
#create GeoTranform from gcp list
GT = gdal.GCPsToGeoTransform(tuple(gcpList))
#Get pixel location from first GCP as a test.
col=gcpjson['0']['col']
row=gcpjson['0']['row']
xp = GT[0] + col*GT[1] + row*GT[2]
yp = GT[3] + col*GT[4] + row*GT[5]
print("POINT ("+str(xp)+" "+str(yp)+" 0)")
##CODE_END
This prints out the WKT 'POINT (-107.18216298 35.0808978834 0)' which is kinda
close to -107.18221364936802, 35.08107313264506 but looking at my post warped
image the chosen pixel is right on top of the intended coordinate so I am
clearly doing something (or a lot) wrong.
Any help would be great.
Thanks,
-Hays
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