[Gdal-dev] USGS vs. ESRI vs. OGR vs Corpscon

[Richard Greenwood]

At 07:02 AM 12/12/2003, you wrote:

>Now we are back to square one so to speak.  ESRI and USGS match each
>other.  OGR and Corpscon match each other.  I've updated the table
>below.  Does NOAA/USGS or NADCON maintain the standards on the
>conversions?
>
>Product Lat                     Lon
>                 DD MM SS.sssss  DDD MM SS.sssss
>USGS            37 11 24.57282  085 54 17.71610
>ESRI            37 11 24.57     085 54 17.72
>OGR             37 11 24.76             085 54 17.62
>Corpscom        37 11 24.75909  085 54 17.61834

I think Frank got it figured out - your USGS and ESRI conversions are not 
applying a datum shift. Simply converting your above lat lons from NAD27 to 
NAD83 produced exactly the same deltas as the deltas between USGS/ESRI and 
OGR/Corpson. So check your syntax in USGS/ESRI (neither are products that I 
am familiar with, although the ArcView 3.? implementation of their 
coordinate conversion tool made this type of error very easy to make). The 
datum shift in meters for your position should be Y=5.742, X=2.411

If you are seeing a difference between NAD83 and WGS84 something is 
definitely wrong. I would guess you are comparing NAD83/WGS84 to HPGN. What 
is the magnitude of the error?

Rich


Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
(307) 733-0203
http://www.GreenwoodMap.com