Projection Help GPS vs National Atlas

[Jeff Portwine]

I don't know very much about this stuff myself, but wouldn't GPS just use
"proj=latlong" ?   So far as I know your GPS would only be delivering raw
unprojected data, so I'd think "proj=latlong" would be all you'd need for
your GPS layer.... then mapserver will automatically project that into LCC
along with your other layers.

-Jeff

----- Original Message -----
From: "James Goddard" <james at GODDARD.BZ>
To: <MAPSERVER-USERS at LISTS.UMN.EDU>
Sent: Tuesday, March 29, 2005 3:20 PM
Subject: [UMN_MAPSERVER-USERS] Projection Help GPS vs National Atlas


> I'm a little confused by all of the projection stuff.  Any help would be
> appreciated.
>
> I'm using the National Atlas maps from
> http://www.nationalatlas.gov/atlasftp.html.
>
> I am able to get the layers I want displayed great.  Now what I want to do
> is add a layer of GPS points.  I am creating a shapefile for these points
> with shapetools entering decimal lat/lon positions.
>
> When I display this layer it the points display but are way off of the US
> map.
>
> I've been playing around with the projections and have yet to figure out
> what I need to get this to display correctly.  Here is what I have:
>
> #main mapfile projection
> "proj=lcc" "lat_1=32" "lat_2=44" "lat_0=38" "lon_0=-
> 100" "x_0=0" "y_0=0" "ellps=GRS80" "datum=NAD83"
>
> #National Atlas layer projection
> "proj=latlong" "ellps=GRS80" "datum=NAD83"
>
> What projection should I use for the GPS coordinates so that they display
> correctly?
>
> James
>