Hot answers tagged

19

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to my own georeferencing experiments a few years ago: http://mike.teczno.com/notes/flea-market-mapping.html It's a bit out of date, but the basic elements are there: find matching points between your image and a reference map (I'd now recommend ...


14

With what understanding I have: Image is an artifact and used in a generic sense, referring to a representation of any real world object. Images may be two-dimensional, such as a photograph, screen display, and as well as a three-dimensional, such as a statue or hologram. They may be captured by optical devices—such as cameras, mirrors, lenses, ...


14

You want the gdal.band.WriteArray method. There's an example in the GDAL API tutorial (reproduced below): format = "GTiff" driver = gdal.GetDriverByName( format ) dst_ds = driver.Create( dst_filename, 512, 512, 1, gdal.GDT_Byte ) dst_ds.SetGeoTransform( [ 444720, 30, 0, 3751320, 0, -30 ] ) srs = osr.SpatialReference() srs.SetUTM( 11, 1 ) ...


13

Unfortunately I can't view that video from Canada but based on the screen shot I believe something like that could be rendered in Pov-Ray. A while back I asked a question about how to generate a high resolution rendering of the globe and @scw suggested I try Pov-Ray. Using this guide I was able to create custom globes with a combination of my own inputs ...


12

If you can, use GIS software, which is designed with this problem in mind: instead of reading the entire dataset into memory, it will only sample the image to create a display and no more. Something like QGIS should allow you to visualize the data, and provides ways of exporting the view, as one approach to creating a downscaled version. Another option is ...


12

Panchromatic images are created when the imaging sensor is sensitive to a wide range of wavelengths of light, typically spanning a large part of the visible part of the spectrum. Here is the thing, all imaging sensors need a certain minimum amount of light energy before they can detect a difference in brightness. If the sensor is only sensitive (or is only ...


10

GDAL has a wonderful file format called VRT, which is an XML wrapper around one or more raster files. One feature of VRTs is their ability to encode square convolution kernels for any given band. It does involve playing around with XML in a text editor (or programatically), but if you're already used to the GDAL tools, it shouldn't be too hard. To ...


10

If there was a shadow in the raw image, say from a tree or tall building, it will still be in the image after the rectification process. Essentially, parts the photo are being stretched or warped to match the position of visible objects in the photo to known places on a map; this will correct for the pitch, yaw, and roll of the plane during the flight, and ...


9

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 ...


9

Let's stop being so square. Why is rectangularity a requirement? It seems like hexagonal grids could also be thought of as a form of raster, as well as an image format if your sensor array is hexagonal. Hexagons have some interesting properties ... why aren't people studying hep-trees like they used to? We're falling behind - extra-terrestrials have ...


8

An alias, in signal processing which is what we're dealing with when we are talking about images, is when a signal is sampled at a resolution that makes it impossible to recreate the original signal exactly. Take this 1-dimensional case: The original signal is the purple sine wave, and the blue dots are where it has been sampled. The blue line is the ...


8

Glovis is one of the best places to start compiling free satellite imagery. For a new user, LANDSAT imagery is a great place to start - you will be able to find data covering the 1970's to present day. There is also a wealth of information available for working with this data. For example, if you are using ArcGIS you can quickly learn how to develop a ...


8

How about firing up an EC2 or rackspace instance and installing the EarthExplorer bulk download application: http://earthexplorer.usgs.gov/bulk/ You could hit the EarthExplorer service with a POST request to submit jobs programmatically: http://earthexplorer.usgs.gov/subscription/submit/ You would need to provide standingRequestName, frequency, ...


7

I would certainly go back to the original image and try rebuilding the pyramids. The fact that it disappears when zooming in to me means it's a pyramid issue. If it persists in ArcMap, do as @scw says, and try GDAL.


7

I found a solution for this. First i convert the image into a vrt layer (gdalbuildvrt) with -srcnodata 0, then i translate it back into a tif file with gdal_translate -a_nodata. Worked fine! :)


7

Some things to consider: 1) Is the aerial imagery going to come stitched together already or are you going to have to manually stitch and post-process each image. You'll probably have to post process the satellite imagery. 2) When was the imagery acquired? For many features (e.g. rock outcrops) you're going to want leaf-off imagery. 3) Was the imagery ...


7

There are published coefficients available for MSS, TM5 ETM+7, QuickBird and IKONOS but I do not believe that anybody has derived coefficients for Rapid Eye. Here is a paper that describes how the authors derived the coefficients for Quickbird (http://www.asprs.org/a/publications/proceedings/pecora16/Yarbrough_L.pdf).


7

You can do this with the Identify tool, just use it to click the World Imagery layer and it will tell you a few things about the imagery, including the date it was collected:


7

Your biggest issue will be that aerial photographs from the 50s may well be in black and white and this doesn't provide good basis for standard classification, such as the tutorial linked by @user3338197 Instead, you will have two paths open for you: Manual digitization (possibly outsourced) Object-based image analysis. The professional standard software ...


6

I find QGis's georeferencer to be pretty decent for a point and click tool. I wrote a little guide - image georeferencing with QGIS - which is slightly Canadian data-source specific, but walks through all the steps you need to get an arbitrary map into QGis.


6

There are a number of places where footprints can come in very handy Public Sector: Taxation: As @Mapperz said, taxation is one area. The percentage of property that is built on is sometimes used as a tax criterion. Planning: Knowing where structures already exist on property can help in the planning process due to applied setbacks and minimum ...


6

if you are interested with RS - Remote Sensing, you can check out Orfeo Toolbox here. following information from their site: a set of algorithmic components, adapted to large remote sensing images, which allow to capitalize the methodological know how, and therefore use an incremental approach to benefit from the results of the methodological ...


6

I've used Enhanced Vegetation Index (EVI) data extensively for analyzing agricultural areas. Although I've never used it with NAIP imagery, all you need is red, blue, and IR data. For your purposes, the biggest advantage of EVI is that it does not "saturate" as easily as NDVI--it offers more contrast (dynamic range) when examining highly vegetated areas ...


6

This can be done in GIMP http://www.gimp.org/ You need to create a custom colour palette - this will read each image loaded and best match to the pixels forcing the colours to become a near as match. You can also restrict contrast and brightness in a similar way http://gimp.open-source-solution.org/manual/gimp-tool-brightness-contrast.html ...


6

UK permits 192 Private Companies [eg EDF], Government Agencies including Police and even the British Broadcasting Corporation [BBC] In the last two years the CAA has required anyone who wants to fly a small UAV in British airspace to apply for permission. The aircraft must weigh less than 20kg and operators have to abide by certain rules. These ...


6

Try this: import os import arcpy bands = [] arcpy.env.workspace = #Set path to dir for r in arcpy.ListRasters(): rObject = arcpy.Describe(r) band1 = os.path.join(rObject.catalogPath,"bandx") #bandx = name of band to extract #outR = # full path to output raster #arcpy.CompositeBands_management(band1,outR) bands.append(band1) #do mosaic ...


6

I found this good discussion at http://www.cartotalk.com/index.php?showtopic=7109 and thought it would be useful to add to GIS.stackexchange for posterity. in ArcMap 10.2, choose > Windows > Image Analysis in the top panel, select the input image in the Processing section, choose the first tool (Clip) this adds a new temporary raster to the TOC right-click ...


6

All of the specific answers I can come up with would have likely already occurred to you as a photographer. A low distortion lens with a shorter focal length (based on your prospective altitude). High shutter speed to minimize motion/vibration impacts. Interval and speed are something of a function of your flight plan and altitude - I don't know if there ...


6

you can find the H and V index in all MODIS product file name. These indices refer to the grid below (from the MODIS Website). For instance you have H8V6 (MOD17A3.A2000001.h08v06.055.2011276103801.hdf).


5

Could be a cloud. Google try to filter these out, but not too well in this case. Have not found any links to back this up, but I do remember reading about it on a post that was looking at the possibility of rendering a 3D real-time cloud layer.



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