25

Aerial photos are continuous data. Each pixel represents the response of a region of a sensor to light directed at it and as that light varies, the response varies continuously. The result is usually discretized (often into 255 or 256) categories, but that doesn't change the nature of the data. Therefore you want to interpolate rather than using ...


14

Landsat is available back to the 80s, it may overlap the dates of your project, excepting of course the 1950s. edcsns17.cr.usgs.gov/NewEarthExplorer/ will let you easily browse the archive, once you apply for a username. With that in mind you could potentially get a series of three satellite scenes, two of which tie in with the aerial imagery. For ...


13

You need to tile the image and add overviews so that the whole image is never read into memory at the same time. GeoServer provides an image pyramid datastore for this purpose. I wrote these notes describing how I set this up on my machine. The key step is to use GDAL to build the pyramid using the following command: mkdir bmpyramid gdal_retile.py -v -r ...


13

This question has been converted to Community Wiki and wiki locked because it is an example of a question that seeks a list of answers and appears to be popular enough to protect it from closure. It should be treated as a special case and should not be viewed as the type of question that is encouraged on this, or any Stack Exchange site, but if ...


12

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 ...


9

Your fire hydrants will have a very unique spectral signature, therefore I would use supervised maximum likelihood classification to classify your raster. An alternative is to run an ISODATA algorithm for an unsupervised approach. Try the following (partial) workflow: Open Iso Cluster Unsupervised Classification in ArcGIS Enter ALL 3 bands (i.e. R, G, B) ...


9

So if I assume the following variables: x = camera sensor x size y = camera sensor y size f = focal length h = height above ground And I am looking for: ay = photo y ground distance ax = photo x ground distance Would these formulas work? making sure that I compare the proper units to the proper units. (h/f)*x = ax (h/f)*y = ay Does this make ...


8

Based on huckfinn answers, few other comments and together with my findings: Winning format is JPEG2000 (why and which version is mentioned below Why not others) Why not others: JPEG Size limitation both data size and dimensions (4GB and 65500x65500) no (internal) pyramids possibility = bigger the image the longer it takes to display it when pan/zoom in/ ...


8

I've found two sources that appear to provide easy to read explanation between Radiance vs. Irradiance and remote sensing reflectance and water leaving radiance. Starting with Radiance vs. Irradiance: Irradiance is simple: exchange of energy (in the form of photons) across a given area of flat surface per time. Radiance is more complicated: exchange of ...


7

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 ...


7

I doubt your process "gets caught in a loop", I think it will just take a long time to complete as your rasters are actually quite large. Those "small rasters totally less than 100mb" are roughly 2Gb uncompressed, each. The layer properties you included in your question show that particular raster has dimensions of 36702 cols, 14147 rows and 4 bands with ...


7

This is a limitation of the PNG format. It only has 3 information channels (RGB), so one of your bands will be suppressed. If you really need to, you can save your NIR band as an alpha channel, but beware - you won't be able to access it easily. Neither QGIS nor ArcGIS allow allocating the alpha channel to one of its display channels. The information will ...


6

This question has been converted to Community Wiki and wiki locked because it is an example of a question that seeks a list of answers and appears to be popular enough to protect it from closure. It should be treated as a special case and should not be viewed as the type of question that is encouraged on this, or any Stack Exchange site, but if ...


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

For topic 2: Here is an longer investigation of JP2, because I was also interested, to use a more efficient compression. And the result IMO is: Within GDAL/QGIS (as a QgsRastrerDataProvider) you can't combine proper jpeg2000 compression and fast caching options like tile sets and block structures in a simple way. Normally I perfer GeoTiff for Raster-DB's, ...


5

I know that this question is rather old, but I wanted to add my 2 cents, in case others come across this thread trying to answer the same question... The previous answers are correct when you truly wish to RESAMPLE your data, such as if you are aggregating your data from a 30 m pixel size to a 90m pixel size. In this case you are attempting to create a new ...


5

I lack the "reputation" to Comment so... If radiometric analysis is going to be performed on the aerial photos then it should be done prior to resampling/projecting. Otherwise you will almost certainly introduce unintended bias into the final product. As per blord-castillo's helpful comment above. If the proximate and final uses of the aerials are for ...


5

MapQuest Open Aerial Tiles Global Coverage (higher zoom level in the US) MapQuest Open Aerial Tile URL example: Terms of Use The MapQuest Open Tiles are available for use for free under the following conditions: http://developer.mapquest.com/web/products/open/map#terms MapQuest Open Aerial Tile URL example: http://oatile1.mqcdn.com/tiles/1.0.0/sat/15/...


5

Please check out http://www.klokantech.com/maptiler/ very good software to create tiles from images.


5

I have been using three different programs for that: AirPhotoSE, VSfm and OpenDroneMap. All of them are easy to work, specially if default values give good results for your pictures. AirPhotoSE is the slowest one (it is an old project that it is not active yet), but it works well and gives good results, both for orthophotos and point-clouds (and even DSMs)...


5

For topic 1. QGIS uses GDAL as an QgsRasterdataProvider. So the capabilities of reading and writing a raster format is implemented by the GDAL lib. You can find supported a format under the following link http://www.gdal.org/formats_list.html. The command gdal-config --formats gives you an overview which format stuff is build into your lib or edition. What ...


5

I can confidently say yes. Add in some surveyed ground control points and you can easily get 10 cm positional accuracy. So far there are two big players that I have been using pix4d is by far the best but it is the most expensive it is really good for editing mosaics. Actually pix4d now has apps to directly work with your phantom and even has a free ...


5

Assuming you have attributes for the polygons for each type (clear cuts, young forest, etc), you can run the Dissolve tool in ArcGIS with this ‘Type’ column as the Dissolve_Field. This will aggregate all the features of each type. If you UNCHECK ‘Create Multipart features’ your result will be a single polygon for each contiguous feature of each type. ...


4

are you in touch with the Nepal community? http://www.osmnepal.org They have quite a lot of projects going on, particularly in the field of Disaster Risk Reduction. Apparently, they have access to higher-resolution images as well: http://tasks.hotosm.org/job/190 (look under the workflow tab) List of curren tasks: http://tasks.hotosm.org/#all/nepal


4

Here a "work in progress" answer... We are currently developing bundle block adjustment support in the orthorectification chain of GRASS GIS 7. It will be usable for aerial photos and UAV imagery. A prototype will hopefully be available in early 2014. If you are interested and willing to test, please contact me directly. It is an enormous amount of work, so ...


4

It's been most of a decade since storing rasters inside an ArcSDE-enabled database was best practice, but if your geodatabase is old enough (though not too old), there may be a simple solution: The sde2raster and raster2sde utilities of se_toolkit were written for exactly this purpose. To export an image, use sde2raster -o export with the split=... option ...


4

What you experience is not an aerial view, but rather a project CRS set to decimal degrees, like EPSG:4326. With that, longitudes and latitudes have different scales, if your working area is far from the equator. To get back to normal view, set the project CRS to a projected CRS. If you use basemaps from the Openlayers or QuickMapServices plugin, this ...


4

If your area of overlap is large enough and the land cover in the scene is homogeneous, you can make the hypothesis that your area is representative. Under that hypothesis, you can use a stratified sample to estimate the marginal error of each class, and weight them based on their proportions in the classified scene in order to predict the overall accuracy....


4

You can use Zoom Earth which allows you to control dates and times. You could also access Remote Pixels Satellite Search. Finally, You can get to the raw data on Amazon Web Services (Landsat Only)


4

You could use this example as a template. You can substitute in any tile server in the form http:{a}.server/layer/{z}/{x}/{y}.png, where server is the url, layer is the layer name, and z, x, y and the zoom, row and column of the globally defined 3857 xyz tileset, which is the standard in OpenLayers, Leaflet, Google Maps and other slippy map server you are ...


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