topic Re: Problem opening ascii grid-file in Data Management Questions

Problem opening ascii grid-file

TomasTomsky — Wed, 06 Jun 2012 07:36:04 GMT

I have a problem When I´m trying to open ascii grid file. When I´m trying to open file, I create pyramids, as Arcmap asks. Then, when it shows as a black box, i use "conversion tools ->ASCII to raster". Then i can get something out. My problem is, how can I set right coordinates in this map? I´m trying to make a visibilityanalysis from viewshed in arcmap. So i need this ascii grid -file, because it contains hightmodels that I need. So I need to add in this file few shapefiles, but all i get is that this new map doesn´t show in same area as other shapefiles. I can see it only if I press "zoom to layer".

Re: Problem opening ascii grid-file

TomasTomsky — Thu, 07 Jun 2012 04:08:04 GMT

I have a problem When I´m trying to open ascii grid file. When I´m trying to open file, I create pyramids, as Arcmap asks. Then, when it shows as a black box, i use "conversion tools ->ASCII to raster". Then i can get something out. My problem is, how can I set right coordinates in this map? I´m trying to make a visibilityanalysis from viewshed in arcmap. So i need this ascii grid -file, because it contains hightmodels that I need. So I need to add in this file few shapefiles, but all i get is that this new map doesn´t show in same area as other shapefiles. I can see it only if I press "zoom to layer".

Problem solved. I had to locate right coordinate system, that was the problem.

Re: Problem opening ascii grid-file

JeffreySwain — Thu, 07 Jun 2012 10:47:49 GMT

Do not forget that you will most likely have to generate statistics to change it from a 'black box' to looking like data is there. The reason for this is that usually ascii files come in with the entire range of possible values. When you apply the standard deviation stretch then the raster will display as expected. Also don't forget the Ascii to Raster tool.

Re: Problem opening ascii grid-file

TomasTomsky — Thu, 07 Jun 2012 11:00:00 GMT

Do not forget that you will most likely have to generate statistics to change it from a 'black box' to looking like data is there. The reason for this is that usually ascii files come in with the entire range of possible values. When you apply the standard deviation stretch then the raster will display as expected. Also don't forget the Ascii to Raster tool.

I did that "standard deviation stretch" and raster displayed as expected. Is it necessary to do "Ascii to Raster", if raster is shown as right?What is the difference?

Re: Problem opening ascii grid-file

JeffreySwain — Fri, 15 Jun 2012 16:48:32 GMT

The ascii file will generally not have statistics created for them, so the default behavior of a standard deviation stretch will not occur so you will have the black box. However, if you use the Ascii to Raster the statistics will be created as the new raster is created, unless you disable it manually. So when this new file is added to ArcMap, it will display as expected. So you do not have to use the Ascii to Raster, but if you want it to display you will have to generate statistics.