I have three themes in the table of contents of my view: Streets, Precincts, and Census Tracts. When I turn on the Streets and Census Tracts themes, they are drawn in the view window, streets appearing on top of tracts.

When I turn on the Precincts theme, nothing is drawn in the view window. The only way to see the precincts is to make the theme active, then zoom to the active theme. Streets and tracts disappear. Neither streets nor tracts (even though they are turned on), are drawn in the view whenever the precincts are drawn. Any ideas? - Jeff Thomas, The Gazette, Colorado Springs, Colo.

Are the themes all in the same projection? I've run into the same problem with one theme being in projected meters and the others in decimal degrees. I believe you can use the Projector extension to convert between projections to make things line up. - Matthew Ericson, The Philadelphia Inquirer, Philadelphia, Penn.

You're describing exactly what happens when the data is in different projections. There is a "projector" extension in ArcView 3+. It can only re-project data that is in unprojected decimal degrees.

I'm guessing you have tracts and streets in decimal degrees (which is the way ESRI distributes data and the way TIGER shows up), but the precincts you got from the government were projected somehow. So you need to find out what projection the precincts came in. Most local agencies use the appropriate "state plane" in meters or feet. Make sure you know whether it's state plane based on the NAD83 or NAD27.

Then you can reproject your tracts and streets to the same projection. Then put all three of them into a View and you should be OK. If your streets/tracts and precincts are all already projected, then projector won't help you, because you need something in decimal degrees to start with.

If you have the just-released ArcView 3.2, it has a re-projector that *can* re-project data that isn't in decimal degrees. So in that case you could re-project each of the themes into whatever you want them to be. It can be run in batch mode if you have several themes to change. For those of us who get a lot of GIS data from local agencies that shows up already projected in a cacophony of projections, this improvement in ArcView 3.2 is a huge help. - Dan Keating, The Washington Post, Washington, D.C.

The story so far: Three themes in my view's table of contents: streets (line), tracts (polygon), precincts (polygon). The problem: Two of the three, streets and tracts, may be viewed simultaneously. But Precincts can be viewed by itself only. And if I move between views of streets/tracts and precincts, I must first "zoom to theme" before the theme may be viewed.

Matthew, Tim and Dan quickly diagnosed this as a projection problem. It appears they are correct. I am told (but am uncertain of how to verify for myself, instruction here is welcome) that both the streets theme, which I got through ESRI's TIGER data service, and tracts, which I got from CEISIN, are in decimal degrees. The precincts theme is in state plane feet, Colorado Central Zone (is this the same as UTM zone 13?), NAD83.

So, based on their most excellent and timely advice, I need to use the projection extension to make the three themes compatible.

Unfortunately, I'm working with a demo version of ArcView. It's a nearly complete version, except, of course, in that it does not have the projection extension and will not accept the addition of any extensions. Jeff Thomas.

I think you can find the projection utility (called Project!) on ESRI's web site. It's definitely included in ArcView 3.2 - David Herzog, Providence Journal, Providence, R.I.

My friends, the NICAR list is the best deal in journalism. Your quick diagnosis of projection incompatibility sent me back to El Paso County's GIS dept., which provided confirmation that the projection of the voting precinct shapefile was not in decimal degrees (as were the census tract and street shapefiles from TIGER and CEISIN), but in "state plane feet, Colorado Central Zone, NAD83."

Dan Keating generously offered to run a projection conversion with his full-blown version of ArcView, but for reasons unknown, the files choked up his attempt. In the meantime, the county's GIS team leader took it upon himself to run a conversion, shipped me the converted files, and all is well. Jeff Thomas.