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#1
HexagonSun

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So I'm having a little problem...
I'm georeferencing some scanned maps. They have the lat/long lines, so I made a spreadsheet with a few intersections to use as control points. However, when I try to display the points (in decimal degrees), they are off. For example, a point in the attribute table has a latitude of -77.25 and longitude of -91.00, but the points that show up are random, like -139, -90.99. Any ideas what I'm doing wrong? The map is displaying decimal degrees, and I chose a projection for the data.
Any help/ideas would be great! I've never added my own points into Arc before, so I'm not sure what else to do.

#2
Crischan

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You probably just loaded the image and assigned an projection? You will still need to georeference the image. Take a look at the Georeferencing Toolbar and it's help.

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Crischan
Crischan Wygoda
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#3
JoeFraser

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That sounds like a false northing and easting is throwing your original points off. Check the projection, and maybe you can subtract the northing and easting from your points so they line up.

#4
haris179

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well...you need to reference the map first, if you tried but lat/long dint show up, it means map is still not referenced.
i use ERDAS IMAGINE for this specially. on the way to referenced map you assign projections, false northing easting everything.

#5
ProMapper

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For Geo-referencing accurately you should first try to find the projection in which the scanned map was designed. If you georeference the map to some other projection system then it will not sit properly on that and generate erroneous lat long readings.

If you want some help then I can try working on it by trial and error to find the projection which may fit best to the scan.

Anu

http://www.mapsandlocations.com

So I'm having a little problem...
I'm georeferencing some scanned maps. They have the lat/long lines, so I made a spreadsheet with a few intersections to use as control points. However, when I try to display the points (in decimal degrees), they are off. For example, a point in the attribute table has a latitude of -77.25 and longitude of -91.00, but the points that show up are random, like -139, -90.99. Any ideas what I'm doing wrong? The map is displaying decimal degrees, and I chose a projection for the data.
Any help/ideas would be great! I've never added my own points into Arc before, so I'm not sure what else to do.






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