# Tag Info

23

Looks like gdalinfo will tell you: A non-georeferenced figure exported from ArcMap layout: C:\Temp>gdalinfo figure1.tif Driver: GTiff/GeoTIFF Files: figure1.tif Size is 244, 210 Coordinate System is `' Metadata: TIFFTAG_XRESOLUTION=96 TIFFTAG_YRESOLUTION=96 TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch) Image Structure Metadata: INTERLEAVE=PIXEL Corner ...

18

GDAL user-friendliness is basically nonexistent, but hot damn does it ever work well. I wrote up this guide to my own georeferencing experiments a few years ago: http://mike.teczno.com/notes/flea-market-mapping.html It's a bit out of date, but the basic elements are there: find matching points between your image and a reference map (I'd now recommend ...

13

Last first: this is the material of regression analysis and statistical modeling. Polynomial regression is discussed in most textbooks. (Draper and Smith treat it in chapter 5.) There really is nothing special (mathematically) about georeferencing compared to Excel's fitting of a straight line to a scatterplot: there are just more variables. (You can ...

13

There are a couple of things to note about the map. First, the lines of latitude are the same distance apart, which means it is in an equirectangular projection. The upshot of this is that neither distances or angles are preserved making it not so useful for navigation. The second point is that it has a scale bar in linear units. Because distances on the ...

12

You want to use the "Spatial Adjustment" toolbar in ArcGIS, it works much like the georeferencing tool, but for vector data rather than raster. It can be applied to an entire layer at once, so you can create just a few control points (they're called "displacement links" in the spatial adjustment tool) and move every polygon in your layer.

11

This questions has been asked a number of times. 30k points, straight up, will not work on an OL map. Or even on a Flash/Silverlight map. Rough (rough!) order of magnitude numbers to remember - 100 points on a JS map (openlayers), 1,000 points in a Flash Map (e.g ArcGIS Flash or Silverlight), 10,000 points on a desktop app (ArcGIS Desktop) are your fine ...

10

No, there is no absolute value for RMS, because it depends on the quality of the map being georeferenced, the quality of the target (base) map, and the purpose of the georeferencing. In particular, any advice that relates RMS to cellsize is misinformed, because cellsize reflects precision in the digital representation of an image whereas the RMS error ...

10

I would suggest talking to your local university or college. I work in a Geography department at a university in the geospatial data centre and we are doing a similar project with aerial photography for our local city. Universities can hire students, or make it apart of the class work. Many profs like the chance to tie their teaching to real world ...

9

Perhaps the easiest way is to use the GDAL tools, which underpin many GIS and mapping systems out there. If you're dealing with lots of files, it is a fairly easy task to write a batch file or script to automate the process. I'll make some assumptions here about your level of comfort with the command line, but hopefully it should be easy to follow. First, ...

8

You could use gdaltranslate. gdal_translate -of GTiff myFile.jpg myFile.tif This will actually give you a geoTiff, not a tiff with a world file. You could also try renaming your 'TGW' file to a 'TFW'.

8

I do know of two web-based solutions that might be worth taking a look at: Map Rectifier from MetaCarta MapWarper created by Tim Waters I'm pretty sure Tim Waters open sourced his code, so even if these particular tools don't suit your needs, looking at their source might give you some insights. Sorry, I can't post more than one external link because ...

8

There are many conventions for image world files. What they share is the image-to-world transformation matrix. (Where they differ is in how the matrix elements are represented and in how the pixels are referenced: more about that at the end.) In almost all cases the world file represents an affine matrix (not the full projective matrix). The affine ...

8

I see them as separate activities. Geocoding is the process of taking coded location information (such as addresses or grids) and turning it into explicit location information (X and Y coordinates, usually). Reverse geocoding is the opposite, taking XY data and locating the nearest address, grid, etc. Georeferencing is the process of taking a raster image ...

7

As far as I know, there's no tool that can directly figure out the projection of a given map, although one would be very useful. What I have done in the past is a bit like the brute-force method, but perhaps a bit more refined. Assuming you know roughly where in the world the map represents, use a site like spatialreference.org (which seems to be down at ...

7

If you're using a recent build of QGIS, you may already have access to the Extract Projection tool mentioned here. From the article: "What this lets you do is to find out what projection your rasters are in. It then exports this to a .WLD file. It also allows you to create .PRJ files. If you have GDAL Tools installed (and activated), you'll find this new ...

7

To easily understand these terms, let's use example of an online mapping service (say Google maps, Mapquest etc.) When you type an address or a placename in the searchbox and in return the map shows a marker at the place. The process of associating an address or a placename with coordinates on the map is called Geocoding. In a spatial database this is done ...

7

If you're using just two points for georeferencing try using "Helmert". Definitely not thin plate spline. The map looks to be for somewhere in England, so set the target CRS to EPSG:27700. Nick.

6

In arcmap 10. I think I would use the footprint feature (in mosaic dataset) and then generate the centroid of those polygons. add an x and a y field to my attribute table, calculate the geometry, then export to dbf and convert to xls. Also found in this answer are several resources for esri help.

6

I don't use ESRI City Engine, but I do a lot of work integrating GIS into 3d or vice versa depending on your perspective. Seeing as nobody gave you an answer, here is a generic approach. What you do really depends a lot on how the model has been built and whether you can get access to it. I will assume you have access to the model or some modelling ...

6

Fitting equations to data is a statistical procedure, so it's best to use statistical software for the purpose. Powerful, easy-to-use software is freely available to all at the R Project. Because the sample data are too limited to show all the essential capabilities of R, for illustrating its use let's add a fourth link matching the "raw" (source) point ...

6

To georeference a vector layer, try the qgsAffine plugin. More info here: Where to find qgsaffine in the menu?

6

When you save your JPEG in GIMP, expand the 'Advanced Options' when the 'Export as JPEG' dialog box comes up. Un-check the 'Progressive' box and then click 'Export'. Your JPEG is then readable in QGIS. "Progressive" changes the encoding to display the image at increasingly higher quality levels until the image is fully loaded. QGIS is expecting standard ...

6

The example map have some kind of Mercator projection (I believe that it is Miller cylindrical projection) with a Greenwich as a central meridian. most Other maps have the same projection or some kind of conical projection (like this one) which parameters you may try to guess. I suppose that Bessel ellipsoid was used for all of them - it was popular in ...

6

I never used this software, but I think it would be very useful for your purpose: Mapanalyst http://mapanalyst.org/. the software is written in java and runs on windows, mac and linux. the author of the software Prof. Bernhard Jenny (oregon State University) is an expert in that field: http://cartography.oregonstate.edu/distortionanalysis.html, so maybe you ...

6

The number of points depends on type of the transformation (and georeferencing is always a transformation) that you need to apply to the image. In the most simple case the transformation is linear and you will need 6 coefficients to perform transformation: x0 = a0 + a1x + a2y y0 = b0 + b1x + b2y where x and y - initial coordinates, x0 and y0 - final ...

6

You have to decide whether you want to enter coordinates in lat/lon, or from a background map with a projected CRS (e.g. in metres). For the first choice, you have to set the target CRS to WGS84 (EPSG:4326), and don't mix up lat and long values. For the second choice, the target CRS must be set to the same CRS as the project CRS. This can be different from ...

6

Well, QGIS is not that good in creating of continuous rasters if that's what you want. Nevertheless it all depends on precision you wish to have in the end. If you wish to trade precision for swiftness - merge them all in GIMP and then georeference resulting image. But be aware that every modification of the raster increases the errors. So if you want to ...

6

In your case (jpg rasters and exact same extent for all rasters) the Warp From File tool is just fine. If you haven't saved a link file yet you should do this first: Georeference one raster in ArcMap, click the View Link Table button and save the links to a text file using the Save button: Then there are different options: Batch: You can use the Warp ...

6

The Map has mostly remarks in French, so I would suggest to use a French coordinate system, and not Everest (who was British). The French used coordinate systems with a prime meridian based at Paris, so EPSG:4821 Voirol 1879 (Paris) is a good start-off. With that, the 100° meridian is hitting the Malaysian coast near Kota Baru, as in your map: You can ...

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