[UW-GIS-L] lat long points not visible on map

[Phil Hurvitz]

You need to be absolutely certain what your original projection parameters
of your points are before you do anything else.  NAD27 and WGS84 are only
datums, and thus are only 1 of the many projection parameters you need to
be certain of.

-P.

******************************************************************************
Phil Hurvitz, MFR | GIS Specialist | College of Forest Resources | 355 Bloedel
Box 352100 | University of Washington, Seattle, Washington  98195-2100, USA
 tel: 206.685.8179 | FAX: 206.685.3091 | e-mail: phurvitz at u.washington.edu
             WWW: http://gis.washington.edu/phurvitz
******************************************************************************

On Fri, 21 Nov 2003, Sacha Vignieri wrote:

> Hi Phil,
> Thanks for getting back to me, and sorry to bother you again, but I am
> still having trouble. I've reprojected the points into the projection of
> the map (NAD27) and the map into the projection of the points (WSG84). I
> also tried reprojecting both into other projections. In both cases with
> no luck. I also tried adding the points in ArcView 3.2, in that case I
> couldn't even zoom to them as a theme.
>
> It seems that it should be so simple...
>
> Any other ideas? I am the lone GIS user in my department and so am
> pretty isolated.
>
> Thanks so much for the help!
> Sacha
>
> Phil Hurvitz wrote:
>
> > Sacha, you probably have defined your prj incorrectly.  Make sure your prj
> > for your points matches the actual data.  If you know the projection
> > parameters for your points, I suggest projecting the data set to a new
> > data set stored in the same projection as the other data you want to use.
> >
> > In addition, sometimes ArcMap attempts to be too smart for its own good,
> > by reading the GeoTIFF headers embedded in images; even when you change
> > the .prj for e GeoTIFF, the embedded parameters override the prj or tfw.
> >
> > I also suggest viewing your data in ArcView 3.x, which lacks the ability
> > to read GeoTIFF headers, and can't project vector and raster data
> > simultaneously on the fly, and can't read .prj files for display purposes.
> >
> > -P.
> >
> > ******************************************************************************
> > Phil Hurvitz, MFR | GIS Specialist | College of Forest Resources | 355 Bloedel
> > Box 352100 | University of Washington, Seattle, Washington  98195-2100, USA
> >  tel: 206.685.8179 | FAX: 206.685.3091 | e-mail: phurvitz at u.washington.edu
> >              WWW: http://gis.washington.edu/phurvitz
> > ******************************************************************************
> >
> > On Fri, 21 Nov 2003, Sacha Vignieri wrote:
> >
> >
> >>Hi,
> >>I am a relatively new user of ArcGIS, although I did take a course in
> >>ArcView a few years ago. I am having a problem getting lat long points
> >>to appear on my map. The map is a mosaic of several USGS DEM quad maps
> >>that has been texturized with DRG data that I purchased online at
> >>MapMart, it is in a NAD 27 projection. The points are sample locations
> >>in Lat Long that I collected with a GPS unit. I have been working in
> >>ArcMap, and am able to successfully add the table and describe the
> >>projection used (by selecting the .prj file I was given with the maps).
> >>When I add the points however, they do not appear on the map. They are
> >>listed first in the table of contents, so they are not hidden. Also,
> >>when I select zoom to event I am able to see some of them (not all), but
> >>not in the same area as the map. I know that the lat longs are correct,
> >>and should overlap with the map.
> >>
> >>Any insight would be GREATLY appreciated, I have been struggling for days.
> >>
> >>Thanks for your time!
> >>Sacha Vignieri
> >>Department of Biology
> >>University of Washington
> >>Seattle,WA
> >>sachav at u.washington.edu
> >>
> >>_______________________________________________
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> >>Uw-gis-l at u.washington.edu
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> >>
> >
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