I need to convert a 30m elevation grid to a grid that gives values for the cell latitude rather than elevation.

I tried converting the GRID to point, adding x,y data to the points, then converting back to GRID using the y-coordinate as the value, however, the large region I am working with is preventing the processes from completing successfully.

Any advice will certainly be appreciated.

Todd

I tried converting the GRID to point, adding x,y data to the points, then converting back to GRID using the y-coordinate as the value, however, the large region I am working with is preventing the processes from completing successfully.

Any advice will certainly be appreciated.

Todd

If so, just set your output extent and cell size (ArcToolbox environment settings or Spatial Analyst toolbar options) to match your DEM then use $$YMAP built in scalar variable in a SOMA/MOMA tool or Raster Calculator expression:

E.g.

C:\workspace\latgrid = $$YMAP

Luke

PS: For info...

Built-in GRID scalar variables:

$$NROWS: the number of rows in the analysis window

$$NCOLS: the number of columns in the analysis window

$$CELLSIZE: the current cell size specified in the analysis environment

$$WX0: minimum x-map coordinate of the current analysis window

$$WY0: minimum y-map coordinate of the current analysis window

$$WX1: maximum x-map coordinate of the current analysis window

$$WY1: maximum y-map coordinate of the current analysis window

$$XMAP: x-map coordinate for the center of the processing cell

$$YMAP: y-map coordinate for the center of the processing cell

Built-in GRID constants.

PI: 3.142

E: 2.718 (e)

DEG: 57.296 (Degree to radian conversion)

GAMMA: 0.577

PHI: 1.618

Built-in grids.

$$ROWMAP

$$COLMAP

I've read your post on this thread, and your thread on the old forums (http://forums.esri.com/Thread.asp?c=93&f=1740&t=182407&mc=6#msgid538607), but I'm struggling to get the $$xmap scalar variable to work with the SOMA tool. It works in the Raster Calculator, but since I am trying to create a model, I need to use the SOMA tool. At the moment, I am trying

$$xmap = (D:\...\Base Data\dem3_4m)

in the "Map Algebra expression" box, and have tried variations including switching the order of variables, spaces and no spaces, no equal sign, etc. I still get an error saying that "$$xmap = is not a valid function or operator." I also cannot find where it would be in the "Usage" listing.

I am currently running ArcView 9.3.1 SP 2 with the Spatial Analyst extension, on Windows 7.

Thank you for any ideas you might have!

I need to create a lattitude grid from the DEM. I have gone through the threads and followed the steps. When I type the statement $$YMAP in SOMA window after setting the extent, working directory and cell size by the spatial analyst > options, i get an error message that "Syntax error at locations 0 of expressions $$YMAP". I even changed the expression as E:\Ph.D\Data_dump\DEM = $$YMAP. How to access these built in functions? Kindly help me sir.

With Thanks

See screen capture attached please.

## Attachments

However, I have had luck using the function "genvecgrid" in the Geospatial Modeling Environment (GME). After generating the vector point grid I added x-y coordinates to the attribute table. Then, created a raster from these points using the y-coordinate field as values. I think I chose a bilinear interpolation technique when doing this.

I have the same Problem as ejjunju ($$XMAP or $$xmap doesn't work in ArcGIS 10)

I want to create rasters with x-Values and do not have a clue how to Do it with the raster calculatur. I could create point-features, use "Add XY" and then convert it to rasters, but as I have to automatize it it seems to be too complicated.

I also have problems finding documentation/ tutorials on Map Algebra syntax. Does anyone know some sources for this

Greetings

Gerald

Unfortunately, ESRI removed those grid functions from 10.0. However, there is a Python alternative, see this link .

Thanks.

Looks like I have to get a little more familiar with Python then.

:-/

Does anyone know Tutorials that make it easier to start with ArcPy?

Greetings

Gerald

For starters, you might want to read "An Introduction to Python and the ArcPy site-package" in the latest issue of ArcUser.

Also, if you want to cast a vote for the reintroduction of the grid functions, go to this link.

Very clever Bill. This deserves its own sticky (if stickies are implemented on this forum).

Bill, thank you very much for this!

I worked out a more detailed implementation of your idea here:

$$NCOLS + $$ROWMAP in ArcGIS 10 Python map algebra

Hi,

I tried to open this link but it did not work. could you please elaborate this. I am struggling to solve this issue as well. Your help will

be highly appreciated.

Cheers

Don't like it that the post number changed -- I thought those were permanent links!

Bill, I am stucked here and anoid that $$XMAP and $$YMAP are removed from 10.1.

I have tried to implement your tip in my raster calculator whitout success. What is wrong? I would like to avoid Python...

xmap = (FlowAccumulation(1) + 0.5)*10 + 500000

ymap = (FlowAccumulation(64) + 0.5)*10

See: $$NCOLS + $$ROWMAP in ArcGIS 10 Python map algebra