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| GeoCommunity Mailing List |
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| Subject: | GISList: Re: [Manifold\ Projection challenge... |
| Date: |
01/11/2002 03:28:30 PM |
| From: |
Robert Heitzman |
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>I've recently acquired a ton of data which I've been
>told is ArcInfo coverage. Mostly vector data.
I think you may be stuck here if the data is in ArcInfo format. Manifold
(and other non-ESRI GIS tools) can sometimes import ArcInfo datya that has
been saved to the .E00 export format. I say sometimes, because the .E00
files are not documented and have to be reverse engineered. Not always a
succesful process.
You'll probably have to get access to ArcInfo to convert the data. I'm not
sure if ArcView 3.2 can import those files.
If you want to get a read only view of the data use ArcExplorer _2_ from
ESRI.
>Secondly, some of the data came to me as *.shp files.
>Upon importing those and overlaying on existing data
>I've got everything in the new .shp files was shifted
>to the south. Quite noticeably too.
Look in the supplied shapefiles for a .prj file. You can import this file
as text into Manifopld (or Notepad for that matter) and read the projection
data for the file as delivered. If the files are from an ArcView 3.x shop
the .prj files may be missing. In that case your only hop is to go back to
the source and beg for the projection metadata. Many folks will just say -
eh? - at that point.
Hopeful the source shop had somekind of standard once upon a time and some
old foggie will remember were it is. He/she may take a swipe at your before
looking however, so keep your guard up!
If the shop was consistant any old .prj file will do as it should in most
cases be identical from file to file if they follow the standard.
>
>I changed the projection of the data to match my
>existing data projection and it helped a little but
>not much.
Almost! Bummer!
>
>Is there some formula or other method I could employ
>to get my new data sources to overlay correctly?
Not that I know of, other than getting the drawing properties defined
correctly. Or tweaking them till it comes out OK.
You say the data is off quite a bit. If 'quite a bit' is a 100' feet or so
it may just be that you are using the wrong datum. A NAD27 to NAD83 shift
is about 100' in my neck of the woods - 120w35n. Try they opposite datum in
the drawings properties and see what happens. (Not Edit, Projection, that
changes the data.) Also if you are not already aware NAD83 and WGS84 are
essentially the same for 2D drawings, at least in the US.
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