POST
|
Margaret, Thanks for the information. I am still new to GIS so I am still figuring things out. I was assuming the transformation happened automatically. After looking into this I figured out why I thought this. The datum's were so close it was hard to really see they were off. I was thinking it was happening automatically since it looked correct. I have since had instances where I did not select a transformation and it was way off. I now know this needs to be done every time. I learn something every day.
... View more
03-31-2016
01:02 PM
|
2
|
0
|
485
|
POST
|
I have found that transformations usually work, but if it does not work this is where your projection tool comes in handy. I had an issue that came up the other day that made me feel really stupid. I was dragging a shapefile on to a raster map layer of Afghanistan. I got the warning telling me a transformation was needed. I let the system conduct the transformation, but it did not appear to be working since the roads were way off when viewing the imagery. I attempted to use the projection tool, only to get the exact same result. I checked the datum, and it appeared to be the correct datum after the transformation and the projection tool were used. Both were providing the same results. In the end, I was so wrapped up in the datum transformation I forgot to take the scale of the imagery into account. The scale at which the imagery was taken was way too small for use with that road layer shapefile and when you zoomed to a larger scale the maps would appear to be way off. Needless to say I learned the hard way after spending a lot of wasted time figuring it out.
... View more
03-15-2016
05:39 AM
|
0
|
0
|
4416
|
POST
|
Mr. Nordhagen, You stated Geographic Coordinate System (GCS) and Datum terminology could be used interchangeably, but from the references I am reading it specifically states a datum is just one part of a GCS. The three parts are an angular unit of measure, a prime meridian, and a datum. I am not trying to sharp shoot, I am trying to ensure there has not been a change to the terminology, or if this is a commonly used expression in the community? I am still trying to come up with my own dumbed down version of what a GSC vs Projected Coordinate System (PCS) is. I thought that your explanation was pretty good, but just wanted to see about the GCS/datum comment. I provided the link below that makes a reference to this in the very first paragraph. http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/What_are_geographic_coordinate_systems/003r00000006000000/ Dennis Patterson General Dynamics Digital Training Instructor
... View more
02-26-2016
09:22 AM
|
1
|
1
|
4416
|
Title | Kudos | Posted |
---|---|---|
2 | 03-31-2016 01:02 PM | |
1 | 02-26-2016 09:22 AM |
Online Status |
Offline
|
Date Last Visited |
11-11-2020
02:24 AM
|