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Author Topic: Map is off North and East (Datum Problem?)  (Read 4289 times)

erik.the.awful

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Map is off North and East (Datum Problem?)
« on: January 15, 2009, 08:12:41 AM »
Okay I have a nice completed map with all the bells and whistles. zoom levels are great, everything shows up on the 60csx fine except it is off by about 1000' North and 500' All the datas have this paralax. When I loaded the shapefiles to compile I used the zandareji and daum it had by default. Is this causing the error? Everything is in proper spatial orientation to one another but the whole map is georeferenced wrong. Any ideas?

-Oz-

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Re: Map is off North and East (Datum Problem?)
« Reply #1 on: January 15, 2009, 09:45:46 AM »
where is this map?  I've never used the zandareji datum; all my stuff is pretty standard wgs84/nad83.

I believe a .mp file has to end up wgs84.
Dan Blomberg
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erik.the.awful

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Re: Map is off North and East (Datum Problem?)
« Reply #2 on: January 15, 2009, 11:43:23 AM »
 :'(

Now that REALLY bites. I needed to import my shapefiles into GPSmapedit in the datum they were created in so it can bound them properly into WSG 84 datum....

ALL of my shapefiles were imported in using zanderji and hence they are off by some number of arc seconds easting and northing. There is no going back to how I had it now since I deleted the original shapefiles for all but the dem data. Now I have to redownload the NHD data and all the others too. I'm going to cry. Crappy mistake to since I have 250 GB of free hard disk space.

Oz,

Do you know which datum all of these are in when they are downloaded? I know for the USA the WSG 84 is pretty standard but does any of it come in a different format? Some of the gov't agencies use others.

One month down the drain, Cest la Vie

-Oz-

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Re: Map is off North and East (Datum Problem?)
« Reply #3 on: January 15, 2009, 08:18:04 PM »
Yea, I back up my data to my external hard drive; guess that doesn't help you.

Also, shapefiles normally have a .prj file that has the datum and all that.  For the standard data in my tutorials I can tell you all the datums pretty easily.
Dan Blomberg
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erik.the.awful

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Re: Map is off North and East (Datum Problem?)
« Reply #4 on: January 16, 2009, 01:01:31 PM »
Well it's okay, Rookie mistake. All the data is easy to get except for the NHD stuff just cause of the weird way they make you request it. Might want to add a note about selecting the appropriate datum in the tutorial under the gpsMapedit section so others don't mess up either.

-Oz-

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Re: Map is off North and East (Datum Problem?)
« Reply #5 on: January 17, 2009, 06:31:53 PM »
I'm adding the datum info to the tutorial now.

Edit: Added to all appropriate sections.
« Last Edit: January 17, 2009, 08:27:29 PM by -Oz- »
Dan Blomberg
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GPS Units: Garmin Dakota 20, Garmin GPSMap 60csx, Nuvi 255W, Nuvi 250W, ForeRunner 110, Fenix 2, Tactix Bravo, Foretrex 401
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