Latest Contributions by SteveRobischon

David, It worked!  I assume the same (extent coordinates in Input coordinate system) applies when you use Same as "feature class"?  And does that mean that if I'm going to use an AOI feature class to define an extent, it needs to be in the input projection and not the desired output projection?  If so, maybe a nice upgrade would be for the Tool/Function to project the extent coordinate system to that of the input on the fly behind the scene before processing the input. Thanks, Steve R ... View more

I'm not trying to just clip the raster. I'm trying to avoid processing a large raster dataset when projecting, and only projecting the portion I'm interested in. This stems from using the National Map View to download NED data. The dataset that comes from the server can cover a much larger extent than the one I'm interested in, so I'd like to be able to project it (so I can do analyses), but only that portion I will subject to subsequent operations. It can take a long time to project the entire raster, and then run the clip (or extract) after it's done. ... View more

I was just trying to make it easier for you to try Dan. It shouldn't matter which extent you set in the environment, unless there's some sort of bug in the tool that only recognizes a processing extent if you set it to a specific raster. BTW, if your AOI shapefile only covers your true area of interest, you will likely experience issues with neighborhood (and other) operations at the edges of the raster. I always start with a raster that is larger than the AOI to minimize these issues. ... View more

Dan, I can't say I automatically click on the environments button, which in some cases has caused a re-do. But in this case, before i posted, I not only tried setting the environment at the tool level, but (independently and in combination) at the application level as well. Neither worked. If I can ask, do you experience similar behavior? Can you perform a quick test where you project a raster, using a processing extent environment of say Same as Display, and see whether the result has an extent any different from that of the input raster? Regards, Steve R ... View more

Melita, Based upon your reply, I messed with the data a little, and now I understand what's happening.  So I guess the bottom line is that, even though you think you're getting on-the-fly projections with ArcMap, when you're working with data with different horizontal datums, unless you explicitly set a transformation, you'll end up in trouble. I remember the graphic the shows projections as proceeding from "flat" back to "ellipse", then across to "other ellipse", then down to "other flat".  So I guess what's now happening is, unless you tell ArcMap to go back to the "ellipse" and across, it just jumps across the "flat"?? Thanks for the help. Steve R ... View more

Hello Tom, I did specify the coordinate system of the input data in the Display XY data window.  The events layer was then created in ArcMap, and as I had not previously set the coordinate system for the data frame, it uses the coordinate system I specified for the input data - the first spatial layer added to the map (e.g. begin with blank map, no data frame coordinate system defined, Add XY Data, specify input data coordinate system (as either NAD27, NAD83, WGS84).  Export resulting events layer to feature class) Regards, Steve R ... View more

Dan, I understand what you are saying about on-the-fly projections, but I'm not sure I agree with  your conclusion.  Consider the process I followed: I started with an Excel spreadsheet containing columns for Latitude and Longitude in an unknown coordinate system I then opened a blank map (so no coordinate system defined for the Data Frame) and added the sheet as a table. I then did Display XY Data, selecting NAD27 as the input coordinate system for the tabular data I then exported the events layer to a feature class named NAD27.shp Next, I closed and reopened Arcmap, and started over with a new blank map (so again no Data frame coordinate system) I repeated the above process, this time choosing NAD83 as the input coordinate system, and exporting the result to NAD83.shp I repeated the process again, choosing WGS84 and exporting to WGS84.shp So at this point, all 3 feature classes have been created independently from the same tabular data.  But since i chose a different input coordinate system for each, and each coordinate system references a different ellipsoid, the physical location of latitude-longitude coordinate pairs should fall on a different spot.  I used the same (literal numbers) coordinate pairs to create all three feature classes, so they should fall on different spots.  40N117E in NAD27 is not the same location as 40N117E in NAD83 - in my part of the country the offset is somewhere between 80 and 240 meters.  By importing the tabular data "independently" in all three cases, the result of the process should have "frozen" the locations of the points at different locations.  The on-the-fly reprojection in ArcMap would then merely project all three feature classes to a common coordinate system, but still at different locations. ... View more