Converty DecDegree XY data to State Plane

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08-08-2011 04:26 PM
TonyLaGreca
New Contributor
Hello,

I have GPS waypoints that are in decimal degree and I am hoping to project these points on some air photos that are in State Plane.  So here is what I have done

1.  I created a shapefile from the tabular data.  While creating the file I said the data was in WGS 84. When I look at this, everything looks right

2.  I Used the project tool and changed the projection to stateplane (South Central Texas NAD 84).  I used WGS to Nad 84 Transform 5. 

3.  I put the resulting shapefile into my map.  The points are way off base.  I looked at the point info and it still has the decimal degree data.  In fact it lines up perfectly with the original non reprojected data. 

4.  I tried to export the data and give it the projection of the data frame.  The exported layer lined up with all of the other shapefiles (ie wrong).

I have done alot of searches on this and seen this question apparently answered by going through the steps that I outlined.  However I have not had any luck. 
I guess that I need to convert my xy data.  It seems like Arc should be able to do this.  What am I missing.  This seems like a simple and often used operation one that Arc should handle in a straightforward manner.  Am I misssing something because I am going from GCS to PCS? 

Any help would be greatly appreciated! 
heywood
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4 Replies
TonyLaGreca
New Contributor
test to see if my subscription works.
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MelitaKennedy
Esri Notable Contributor
Hi,

You certainly seem to have done all the right steps!

When you looked at the point info in the output shapefile, did you look at the attribute table? The attribute table isn't updated when a dataset is projected because we don't know if you want those values updated. The actual values are stored internally.

Add the output shapefile to a new ArcMap session. What is the data frame's coordinate system set to? You may want to also check the map units (data frame properties, general tab) as the map units reflect the data frame's coordinate system. If you then change the display units to degrees, you can check that the points are in the right location.

How far off is this data relative to the photos? A few feet or meters? Hundreds of meters? Or Kilometers away?

Can you post a sample lat/lon point, plus its corresponding state plane coordinates?

Thanks,
Melita
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TonyLaGreca
New Contributor
Melita,

I was hoping you would respond.  I read other posts that you helped out on and it seems you are the one to ask.  Thanks.

Here are some of the waypoints straight from the GPS.  As far as I can tell they are in dec degree.  Wait I am getting a flash back from cartography 101 aren't DD in the western hemisphere supposed to be neg?  I will check this out could be my problem.
Waypoint_Number Date          N           W          Z
139 23-MAY-11 3:16:23PM 29.92288 95.48129 108
140 23-MAY-11 3:21:16PM 29.92346 95.48135 110
141 23-MAY-11 3:21:26PM 29.92345 95.48135 111



Ahhhaaa!  that worked beautifully.  I had two things going wrong (as usual my own dumb mistakes)  first I had the N and W and the X and Y backwards when I was importing the points to a shapefile.  Second I needed to put a negative sign in front of the W values. 

Sorry for wasting your time.  Thanks for your help (both here and in the previous posts).

have a great day!
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MelitaKennedy
Esri Notable Contributor
I'm just glad you've got it working!

Melita
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