In the first scenario. before opening your scan in MI lay out on it a grid
that approximates what you think is an apropriate scale in your desired
units. Rescanning may be appropriate after this but may not be necessary.
Pick 4 or more of your grid points spanning the area of your map (at least
the 4 corners) and when you open it in MapInfo choose to register the image
and use the values of the points you have laid out on your map. Non-earth
would be your projection. And you should be set to go.
Second scenario: If you have a few points and you know the projection,
especially if it is state plane, you should be able to carefully, manually
obtain and place on your paper map points with coordinates appropriate for
registering your scan. You want at least the 4 corners and the more the
better. use these points to register your scan when you open it in Mapinfo
choosing the projection and units you know to be correct. Nothing on the
scanned map will have coordinates as vector objects within MI unless you
then digitize those objects on-screen. However, any work that you then do
will be within the coordinate system you have set up. This is a standard
way to work. YThe more and accurate points you use the better. The only
significant pitfall is the panning/screen redraw/object location BUG within
MapInfo which they dont seem to want to address.
Regards
George M Smith
At 07:02 PM 3/10/99 -0700, you wrote:
>Hi,
>
>Two scenarios:
>First:
>A drawing from an old report whose only clue to a coordinate system is a
>graphic scalebar. After scanning the drawing, then importing it into MI;
>how can you create an approximate coordinate system (like Non-Earth) that
>will allow you to make approximate measurements after you've digitized the
>map features? There are no electronic versions available; no point
>coordinates indicated on the map. It's large scale so no worries about
>curvature of the Earth.
>
>A second perhaps easier problem:
>If you have a CAD drawing on paper which has a few points labeled with
>coordinates (say State Plane). Can you just input those coordinates in the
>dialog when you register the scanned image and voila, the map and all its
>features have a coordinate system? (Provided of course that you're lucky
>enough to have the points distributed relatively evenly) As you digitize
>and save features as separate MI tables will each have some semblance of a
>coordinate system? Where are the pitfalls in this scenario?
>
>Thanks for the help,
>
>Phil Uhl
>Salt Lake City
>
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