Listers,
Am I correct in thinking that two maps, one done in Lat/Long, the other in
SPCS NAD83, should appear in their correct relative positions when opened in
the same MI window, given that MI reprojects on the fly? Let me explain.
We purchased some commercial environmental hazard data, which came in .tab
files whose projection was Lat/Long. However, the hazard points plot
approximately 250-300 ft east of their correct positions on our NAD83 base
maps. This offset seems identical to the predicted offset between the SPCS
NAD83 and SPCS NAD27 datums.
Is it possible that the original hazard data was geocoded against a street
map whose projection was given as NAD83 in the header, but whose coordinates
were actually in NAD27? Presumably this data was reprojected into Lat/Long
coordinates before being delivered to us.
Does this make sense? Are there other possible explanations?
TIA.
____________________________
Tim Warman
Geologist & GIS Specialist
Richard C. Slade & Associates
North Hollywood, CA
(818) 506-0418
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