GNSS control to OPUS to state plane
An OPUS position in ITRF2020 to NAD83(2011), then state plane coordinates, the orthometric height, and the combined factor for ground distances.
Step 1
Transform between NAD 83 and ITRF or WGS 84
OPUS reports ITRF2020 at the observation epoch; bring the point to NAD83(2011).
You should see The frames differ here by 1.4406 m horizontally, toward 110.9°.
Step 2
State plane zone lookup
Which state plane zone the point is in.
Carries latitude from step 1, longitude from step 1.
You should see Found 2 zones.
Step 3
Latitude and longitude to state plane (SPCS83)
Northing and easting in Colorado Central (0502), in the zone's legal unit.
Carries latitude from step 1, longitude from step 1.
You should see In Colorado Central (0502) the point is at easting 3,143,344.231 US survey ft, northing 1,694,533.8 US survey ft.
Step 4
Ellipsoidal and orthometric height
The ellipsoid height as a height above the geoid (EGM96 here; US work usually uses GEOID18).
Carries latitude from step 1, longitude from step 1, height from step 1.
You should see The converted height is 1,607.854 m. The geoid is -16.993 m above the ellipsoid here.
Step 5
Combined scale factor (grid and ground)
Grid scale and elevation factor together: how 1,000 ft on the ground reads on the grid.
Carries grid scale factor from step 3, ellipsoid height from step 1.
You should see The combined factor is 0.99974828. A ground distance of 1,000 US survey ft is 999.748 US survey ft on the grid.