autocadqgis
I am using QGIS to open mrsid files from NAIP, clipping the part of the county that I need and using the "save as" option to export as a geotiff in state plane coordinates for use in Autocad. I am having a few issues with this method:
First, the resolution on the image is not great.
Second, the insertion point comes into Autocad correctly but when I close the image correlation dialogue box the image rescales for some reason.
I can rescale the image, but am wondering what I'm doing wrong?
AutoCAD LDD, Civil 3D, Land Map Desktop, etc, are all capable of interfacing with spatial data directly. If I'm understanding your question correctly, bringing in spatially referenced rasters and (shapefiles) is quite an easy process.
As I said, If you have a "Map Capable" version of CAD, just georeference this image in ArcGIS, and update the georeferencing (I suggest a refresh in Catalog just to be sure it takes hold). Then, open CAD and type "mapconnect" in the command line. The rest should be easy to figure out (from here you'll attach a raster image and you should see that option in the window that opens in CAD). When you route to your geotiff and add it, it will be to scale & proper location. You may have to select it and order it to the back (it usually covers the drawing layers that are present in the drawing). I am making the assumtion that you have a map capable version of CAD. If you need further explaination let me know.
This works the same with vector data. That command will also allow you to connect to shapefiles. The command "mapimport" does the same thing, but brings the data in as AutoCAD features with no attribution.
If the original images are in an autocad drawing and they are in the correct position, angle and scale.
You can use raster design to export the image with georeferencing. Not sure if this functionality is available in raster without having map3d or civil 3d installed with it.
I suggest using tif format as geotiff will be most usable in autocad and arcmap.
My MO is packbits/tiled/geotiff.
If you don't have the geotiff option in raster design.
the esri method is there but I don't like it as well.
insert the image into an arcmap (no layout view) dataframe (use the add data butoon).
zoom to the area the image "should cover".
open the georeferencing tool bar.
With some reference data (some known points on both the data and the image, hopefully in the [projection] coordinate system of the image)
click the fit to display button. (you may have to resize the display and click again several times).
Then use the
shift
rotate
scale
buttons to get the image exactly where you want it. (this is cluncky compared to map3d).
Note that you may need to utilize the control points tools if you can't match the existing image projection closely to a CRS (utilizing only move , rotate, and scale). this will squeeze the image into a crs.
and autoregistration sounds great huh?!
You should take care with this and not save over your original. If you have to use this I suggest using the esri help for a tutorial on the subject. But remember to use the outside edge and go in a clockwise direction for your control points.
When the image looks like you want (in the correct location, rotation, scale) use the update reference button to write the new georeference data into the file.
Or alternatively use rectify to write an entirely new image using an algorithm to resize the cells to your new unit and crs.
Best Answer
As an alternative to
Save As ..., you can tryRaster -> Conversion -> Translate. It allows you to rescale the output as well.If you need a different coordinate system, you have to use
Raster -> Projections -> Warp.I'm not sure what units of measure Autocad uses, QGIS uses degrees, meters or feet, depending on the layer's CRS. You can create a custom CRS that uses other units if needed.