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

[Jeff Hepinstall]

Sacha,
  Are you sure that you had defined the projection of the original 
points (PROJECTDEFINE in arc command line, or Define Projection in 
ArcToolBox) before you tried to project them? Are you using Clarke1866 
as your Spheroid when projecting to NAD27? (your reference to WSG84 
below makes me thing you are mixing up two datum-spheroid combinations). 
Can you provide the parameters for 1) the lat/long coverage, 2) the DRG 
data (by parameters, I mean: projection, datum, spheroid, zone, units). 
Thanks,

Jeff

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
>>>
>>> _______________________________________________
>>> Uw-gis-l mailing list
>>> Uw-gis-l at u.washington.edu
>>> http://mailman.u.washington.edu/mailman/listinfo/uw-gis-l
>>>
>>
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>
>
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-- 
Jeffrey A. Hepinstall
Faculty Research Associate
Box 352100
Urban Ecology
University of Washington
Seattle, WA 98195-2100
(206) 293-3237 (cell)
(206) 685-9795 (fax)