Imagery refers to raster based datasets acquired from sensors on satellites or aircraft.

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21
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7answers
2k views

Work flow for georeferencing imagery using open source tools?

Does anyone have a recommendation for a work flow for georeferencing high resolution aerial photography using open source tools? Comparison of user friendliness and robustness between Quantum GIS ...
13
votes
3answers
517 views

Alternative vegetation indices

I have been using NDVIs with limited success to identify trees in the central Great Plains region of the USA. The problem I have been encountering is that reflectance from farm fields/pastures have ...
12
votes
4answers
455 views

When should I be calling a 'rectangular grid of pixels' a raster or an image?

Reading through GIS literature, it sometimes feels that authors use the two terms with a specific meaning in mind. I always treat the terms interchangeably. Am I wrong? Read the first line in the ...
12
votes
2answers
440 views

Is there a programmatic way to retrieve Landsat 8 Satellite Images?

I have not been able to find out this myself, but is there a way to programmatic access Landsat 8 Satellite Images? I know that I can go to USGS EarthExplorer to search and browse through the scenes, ...
12
votes
2answers
898 views

How to equalise colour, brightness and contrast across several scanned paper maps

I am a vectors guy mostly, but for a current project I need to work with a bunch of old scanned paper maps (ww2 bomb damage maps for London, if your interested!) We scanned and georeferenced the ...
10
votes
1answer
181 views

How did Nova create the globes in Earth From Space?

Nova recently aired Earth From Space on PBS. (I highly recommend it.) Also found here on youtube. Produced in extensive consultation with NASA scientists, NOVA takes data from ...
10
votes
6answers
946 views

What is this “brown spot” in Google maps?

I was in Google maps today and noticed near Baltimore, US where the river is, there's a huge brown spot. Is this due to all of the waste? If so, will this keep going all the way into the ocean?
10
votes
2answers
599 views

What countries allow commercial use of drones to collect aerial imagery?

Currently the US government forbids commercial use of drones to collect aerial imagery. The FAA is supposedly reviewing this to determine what sorts of restrictions are needed to allow this to happen ...
8
votes
4answers
961 views

How can I work with 3+ Gigabyte TIFF Files?

While I don't work in GIS myself I'm trying to support one of our users here who looks after all our mapping and GIS data. We've received a 3.2GB Tiff image containing satellite imagery of our site ...
8
votes
3answers
287 views

Where can I get aerial images for commercial use?

Related question: Free aerial map images for commercial use - Alternatives to Google maps I'm looking for a service that will allow me to download images at up to 1 meter resolution. Currently our ...
7
votes
4answers
689 views

Where can I download free satellite imagery of Cambodia for offline use?

I am an entry level GIS user - I have had one semester of GIS in college. I have successfully downloaded raster satellite imagery from Seamless (tiff files) for my class project. Now I am trying to ...
7
votes
4answers
589 views

Visualization of satellite image - directly in python

Is there any way (a package or what not), to visualize a geotiff image directly in Python? I don't want to use ENVI or ArcGIS or anything else. Thank you in advance.
7
votes
2answers
256 views

Practical Building Extraction Algorithm Implementation

I've been reading many papers over 3D building extraction using LiDAR data and Aerial images. I see that there are many different algorithms for doing such things, such as this and this. Those ...
7
votes
3answers
1k views

Use of Pictometry images in GIS

I am wondering if anyone has worked with Pictometry in GIS and their .pmi files. I recently acquired imagery from them for my area and have discovered that I cannot add the pmi files to the webmap, I ...
7
votes
2answers
271 views

How to perform enhancement operations on an satellite imagery in QGIS?

I am a new user of QGIS please suggest how to perform image enhancement operations on an satellite imagery like ratioing, contrast stretching, edge engancement, filtering etc. in QGIS?
7
votes
3answers
1k views

Poor image quality of raster pyramid files in ArcGIS (no anti-aliasing)

There are several GeoTIFF files (size ~7000x7000 px) which I try to open in ArcGIS Desktop 10.0. I have already created raster pyramids for them (.ovr files) using geoprocessing tool but their quality ...
7
votes
2answers
2k views

Does an open source alternative to ESRI's Image Server exist?

I noticed the default way to store imagery is by using a database in the open source world. I like ESRI's Image Server software because it removes the need for a database and makes backing up a lot ...
6
votes
4answers
5k views

Spatial resolution of Google Earth Imagery

What is the spatial resolution of imagery used in Google Earth? At various places on the web, I have been reading it varies from place to place - 60 cm, 2.5 m, 15 m and so on. I was wondering if there ...
6
votes
3answers
168 views

Best practices for identifying training sites

Prior to image classification, collection of training sites and obtaining a signature file is the most critical step. Field visits with a reliable GPS Unit is usually the first step followed by ...
6
votes
1answer
320 views

Coordinate system in aerial imagery

I am calculating WGS84 coordinates of points in an aerial image, given the WGS84 coordinates of the center of the image and the ground distance width and height (calculated from altitude and lens ...
6
votes
1answer
1k views

What causes these shiny artifacts in Google Maps imagery?

Do you know what causes artifacts like this one: Source: ...
5
votes
2answers
864 views

Creating a multispectral image from scratch

I want to make a multispectral image from cero to do some tests on it. Something really simple like 5 completely uniform bands with salt and pepper noise on them or a square of different values at the ...
5
votes
3answers
739 views

How to crop a satellite image?

I am wondering how to or if it is possible to crop a SPOT satellite image (the image has black edges) using ArcMap 10 and if so how do you do this. I appreciate any advice.
5
votes
1answer
327 views

50cm imagery - aerial or satellite?

The area of interest is 1450 km2. My options are: 50cm newly collected aerial natural color imagery for $28,300 OR 50cm recent archival satellite imagery (includes near IR band) for $20,600 The ...
5
votes
5answers
796 views

georeferencing aerial photos with only known centroid

I have heaps of aerial photos that need to be georeferenced. I have access to ArcMap and ERDAS. All I am given is an excel sheet with the centroid coordinates of each image. Each photo covers an ...
5
votes
5answers
4k views

How Do You Remove No Data From A Raster (.sid)?

I have an Image.sid that has a white border which is No Data. I've tried using Clip Raster Tool with no success. I've also changed the symbology value for No Data to be transparent. I'd like to ...
5
votes
2answers
229 views

Wavelet vs Discrete compression for imagery

What is the main reasons to choose wavelet (jp2, sid, ecw) instead of discrete (JPEG) compression methods for raster data? Lets limit this question to aerial imagery and lossy compression. Why ...
5
votes
1answer
53 views

What lens and camera settings are recomended for UAV (drone) aerial imagery capture? [on hold]

I have been toying with the idea of purchasing/bowrrowing a UAV and attempting to capture my own aerial imagery. I have pretty good DSLR Canon gear and several lenses but I am wondering what lens, ...
5
votes
2answers
317 views

Extract certain area of contours/satellite images

I have 2 satellite images (jpeg2000 format) and 2 xyz-files from the same area. I am trying to extract certain region from the area including contour lines and the satellite image in order to import ...
5
votes
2answers
263 views

Which is the best way to create a polygon with the extents of a raster file in QGIS?

I have a tiff image file and want to get a polygon with the extent of the tiff. Is there a direct way of doing this? Right now i have to convert the image to vector (with gdal_polygonize) and then ...
5
votes
1answer
101 views

Non-Research Transportation Raster applications

My experience with rasters is pretty basic. 99.95% of what I do involves vector and transportation modelling. In research, there are numerous transportation applications using rasters and imagery ...
5
votes
3answers
1k views

Mosaicing many large ECW files for display in ArcGIS Server apps

I have about 200 ECW files of recently acquired 1-foot resolution aerial photos. Its about 15GB worth, covering over 250 sq. miles. Unfortunately, you need a license from ER Mapper that runs about ...
5
votes
1answer
209 views

Pictometry Accuracy and/or Alternative

I'm looking for some insights into the accuracy (x,y,z) of oblique imagery from Pictometry in terms of providing accurate measurements for property evaluation. Is the high cost of this product ...
5
votes
1answer
337 views

Is there any plugin for QGIS to calibrate contrast and brightness of a raster layer?

I frequently need to deal with the contrast and brightness of raster layers in QGIS and I miss the tools in ArcGIS for this task. Should there be a plugin already developed for QGIS? If there is, ...
4
votes
1answer
89 views

Do OrthoRectified Images have shadow?

Orthorectified images have removed relief displacements and tilt displacements. Since the assumption of orthorectification is to keep the light source at infinite distance so that the light rays are ...
4
votes
2answers
152 views

Purple anomaly on imagery

Can someone please tell me what this purple anomaly is on the imagery that we just received. The only thing I have done processing wise is to build the pyramids when they first came into ArcMap. Other ...
4
votes
3answers
465 views

Image viewer or browser for large images

I have some big images. I'm looking for an easy way to browse and view them. Currently I'm using Preview.app on OS X, but it wasn't designed for these types of images. My images are, for example: ...
4
votes
1answer
446 views

How to identify image location?

I have a satellite image of only one part of some city with a lot of vegetation. I need to find out where is that image taken. I'm interested is there any way to find out where it is taken on Google ...
4
votes
2answers
177 views

What does MODIS data reflectance values (MOD13Q1) mean?

Several publications suggest filtering MODIS data (in my case MOD13Q1) prior to use. They recommended to filter out pixels having blue reflectance more than 10%, but what 10% here means? is it 10% of ...
4
votes
2answers
163 views

Unrestricted codec for creating raster files with interior pyramids files

I'm looking for a tool that will allow me to mosaic a collection of images into a file format with performance similar to MrSID or ECW, but without the licensing restrictions that those formats come ...
3
votes
3answers
2k views

How to redefine the nodata value into zero in QGIS?

I have an image which i cliped with an AOI polygon. The contour area was set to pixel value = 0 and I have a nodata value of -32768. I want to redefine the nodata value into zero. I used to do this ...
3
votes
2answers
258 views

Tasseled Cap Transformation Rapid Eye

I want to do tasseled cap transformation on rapid eye data. the main question would be about the parameters which are used. Somebody has a suggestion?
3
votes
2answers
98 views

How many stereo satellite imagery required to prepare DEM of an area?

I want to know how to find the nos. of scene of stereo CARTISAT-1 data required to prepare DEM of an area(say 84000 sq km)? any suggestion/solution/calculation?
3
votes
2answers
346 views

Third party base layer other than Google map

Can we use third party base map (images tiles) for displaying vector data?, like we use google map as base layer for displaying vector data in OpenLayers application.
3
votes
3answers
308 views

Which Software can derive building footprints from imagery?

I'm looking for a software solution that can process large areas of imagery to produce building footprints. For the area of interest, I can source either satellite stereo pairs or oblique imagery. I ...
3
votes
4answers
176 views

Place image without using points in QGIS

I am trying to find a GIS software that does this, so I am trying QGIS but other suggestions are welcome. I have a basic shp boundary such as a rectangle. I want to be able to import an unreferenced ...
3
votes
2answers
312 views

Purpose of building footprints

What are the uses (public and private industry) of building footprints? I'm trying to figure out how polygon building footprints can be used. i.e. are they used for determining tax liabilities, ...
3
votes
2answers
82 views

Geographically georeference image with limited information

It is possible to semi-accurately georeference an image given only the following information? I'd like to do this programmatically. Center point of terrain, Lat/Lng (WGS84) Pitch of camera FOV ...
3
votes
2answers
88 views

Google maps white striations / false artifacts

What are the common white striations running from NW to SE visible when you zoom in around 5mi scale? For example at (+81, -80)? But they appear 'all over'. Are they snow drifts? or satellite sweeps? ...
3
votes
1answer
268 views

Is there a way to export online ESRI basemap layers to raster?

I have been working on polygonizing the vegetation areas in some counties from imagery. When I have the mosaic raster locally I can easily get the polygons using Image Classification Toolbar. But when ...