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Thanks for your help! Finally got it to work testing both methods. The final .tif output was intended to be imported into a georeferenced Civil3D .dwg file, so keeping the file size down was important since I've noticed Civil3D refuses to import .tif images over about 700MB. Matt
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06-01-2016
06:41 AM
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Apologies if this is a simple question, but it's the first time I've really needed to do this. I'm using ArcMap 10.2. I have a large raster mosaic I created using four image tiles, but the extent area for my project (which falls at the intersection of the four tiles) is only about 25% of the full image. I am trying to extract a new raster dataset (.tif) based on a polygon I created. Here's the problem: After looking at several tools (Clip, Extract Raster), I find that the *entire* extent area of the original input raster is preserved as "No Data" cells for the areas that fall outside my polygon mask. To enhance performance and reduce file size, I would simply like to create a smaller raster "without the baggage of the original extent". Ideally, my end result would be a reduced-size, reduced-extent raster based on the satellite view shown below. Can anyone tell me which tool to use in order to accomplish this? Or perhaps I am not selecting the correct settings in the tools I used? In the image below, the black area represents the full-extent raster, and the satellite imagery is what I want to export as a stand-alone raster. Everything I've tried still preserves the original extent in the output file. Any help would be appreciated! Thanks!
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05-31-2016
07:01 AM
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Hello everyone, I've been experiencing this problem for over a year now, but it's become extremely bothersome now that I'm working on the "heads-up digitizing" of large extent areas. It seems that compared to accurately verified survey points and USGS image tiles, ESRI's base imagery simply does not align with the same accuracy. Through many projects, I have verified the proper projections of both survey data and georeferenced imagery downloaded from the USGS (both of which align perfectly ontop of each other), but turning on the Bing base imagery shows it can be mis-aligned as much as 10 feet in some instances - even when the data frame is projected in the same coordinate system as the survey data and georeferenced imager tile. For small projects, this does not matter for me - since one or two USGS image tiles give the accuracy I need. With larger projects, however, extending hundreds of miles - I simply don't have the time or physical disk space to download accurate USGS imagery. Instead, I must rely on Bing base imagery to trace my features (in this case, railroad tracks). The attached picture shows a new MXD, with simply the USGS image tile imported. This ensures ArcMap imported the projection of the image tile since it was the first feature added to the map. Then, I turned on Bing base imagery: The image above shows the edge of a USGS image tile, shown over the background of Bing imagery in ArcMap. As you can see, the features don't line up - the railroad tracks, the right-of-way, the vegetation zones, etc. While this example is just east of Sidney, Ohio, USA - this seems to be a problem in all parts of the continental United States. I have rarely, if ever, seen the Bing imagery "spot on" with properly referenced imagery or survey data. What am I doing wrong, if anything? Suppose I created a complex network of features that were traced using the Bing base imagery. Is there a tool to reproject these features to a more accurate spatial location? Thanks for any and all help!
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07-02-2015
11:09 AM
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Hello all, I'm having an issue with geo-referenced mosaic imagery being extremely large after importing into Civil3D from ArcMap. Hoping some people here can chime in on a possible way to fix this issue. The current workflow I'm going through is downloading imagery from USGS Earth Explorer, georeferencing said imagery into a new projection in ArcMap, and then importing that imagery into Civil3D so our CAD drafters can begin work on a new .dwg basefile. For the scope of some of our projects, the imagery can sometimes be a mosaic of four separate images. This is causing major problems for my co-workers who work in Civil3D, as the base imagery for them to begin their drafting can bring the .dwg file to an unreasonable size. While the .dwg itself seems to be reasonable in file size (3,000 or 4,000k), the mosaiced, georeferenced imagery being put into the file is (in the case of four tiles) 392MB in size. This is seriously causing a choke in our workflow, particularly as we export Civil3D drawings into PDF. The drafters have created "viewports" only showing a small section of the imagery (our final output can be several PDF export sheets showing different areas of our engineering designs), but each PDF still exports at around 9MB in size - way too big for the purposes of our organization and client specifications. Even "clipping" the imagery to our area of focus doesn't seem to help, as the file sizes for the exported PDF documents remain the same. Can anyone offer any tips or techniques that might allow us to substantially reduce the file size of the imagery, yet not compromise resolution? Thanks!
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06-16-2014
06:44 AM
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