Hi Amira, I love this question! Seems to come up every few years.
First, see this:
<http://gis.washington.edu/phurvitz/gis_data/projection_exercise/>
If you are using ArcGIS Destkop, then add to a data frame your suspect
layer and one that you know to have the correct projection definition.
Clear the projection on the data frame:
<http://gis.washington.edu/phurvitz/gis_data/projection_exercise/>
Which will then place your data in a generic Cartesian coordinate space.
Zoom to the known layer and note the coordinates as you move the mouse
around. Then zoom to the suspect layer and do the same. The magnitude of
the coordinates may give you enough information to make a wild guess if
you are know what to expect for your study area in different
projection/coordinate systems. If your data are within WA, the
projection checker files in my exercise may help.
Now add one layer from each of the known projections along with your
suspect layer, clear the data frame's projection, and if your suspect
layer overlaps as expected with one of the trusted layers you may have a
match. It is important to clear the data frame's projection because
ArcMap's default behavior on a data frame with no projection is to reset
the data frame's projection to the first added layer that has a defined
projection.
Once you have discovered the actual projection/coordinate system of your
data set, you can use ProjectDefine to correctly tag the data set.
Beware of subtle differences, such as NAD27 vs NAD83 or HARN/HPGN that
can show up as systematic but small shifts in XY.
Bonus question 1: what is the difference between Project and ProjectDefine?
Bonus question 2: Does ProjectDefine change any of the XY values of
points or vertices in a vector data set?
-P.
**************************************************************
Philip M. Hurvitz, PhD | Research Assistant Professor | UW-CBE
Urban Form Lab | 1107 NE 45th Street, Suite 535 | Box 354802
University of Washington, Seattle, Washington 98195-4802, USA
[email protected] | http://gis.washington.edu/phurvitz
"What is essential is invisible to the eye." -de Saint-Exupéry
**************************************************************
On 10/05/2017 12:01 PM, anchowyu wrote:
Hello, I have a seemingly simple problem that I cannot figure out.
My layer properties states that my layer is in the correct projected
coordinate system but it is not projecting accurately with my other
layers. All my layers and data frame are in the same projection.
I’ve tried doing the Project and Define Projection tool on this layer
and it still remains flat and nowhere near my other layers.
Can anyone help? I am not sure what else to try. I can send my file too,
it’s small.
Thank you!
*Amira Chowyuk*
Graduate Research Assistant
University of Washington – Seattle
SEFS, Biofuels & Bioproducts Lab
e: [email protected] <mailto:[email protected]>
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