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

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27
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7answers
3k 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 ...
16
votes
4answers
4k 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, ...
15
votes
3answers
1k 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 ...
13
votes
4answers
637 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
2k 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 ...
11
votes
2answers
907 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 ...
10
votes
1answer
292 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
1k 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
530 views

Calculate potential of solar radiation on rooftops (without LiDAR data)

I'm trying to calculate the solar radiation for rooftops, but I have a big problem, I don't have LIDAR data. I need to give the buildings the information of height. I've tried to do these, but for a ...
10
votes
3answers
446 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 ...
9
votes
2answers
2k 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 ...
9
votes
4answers
1k 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
4answers
2k 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 ...
8
votes
1answer
507 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 ...
8
votes
3answers
2k 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 ...
8
votes
2answers
412 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 ...
8
votes
3answers
2k views

Poor image quality of raster pyramid files in ArcGIS Desktop (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 ...
8
votes
3answers
11k views

Where can i download a good World image in GeoTIFF?

I can either be from MERIS (ESA) or from MODIS (Nasa). I already reached these sites: http://www.unearthedoutdoors.net/global_data/true_marble/download ...
7
votes
5answers
2k 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
1answer
3k views

Panchromatic Image association with high spatial resolution

How and Why is a Panchromatic Satellite Image associated with high spatial resolution? I googled and found that it is a single band image, but then why is it called pan-chromatic(All Colors). Does it ...
7
votes
4answers
14k 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 ...
7
votes
1answer
3k views

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

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, ...
7
votes
3answers
201 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 ...
7
votes
2answers
1k 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
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
5answers
1k views

Georeferencing aerial photos when only centroid is known using ArcGIS for Desktop or ERDAS Imagine?

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 ...
6
votes
2answers
400 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 ...
6
votes
2answers
903 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 ...
6
votes
1answer
775 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
2k views

What causes these shiny artifacts in Google Maps imagery?

Do you know what causes artifacts like this one: Source: ...
5
votes
3answers
2k 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
6answers
8k views

Removing No Data From Raster (*.sid) using ArcGIS Desktop?

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
3answers
708 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: ...
5
votes
2answers
388 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
86 views

Is it possible, and if so how, to effectively classify vegetation types using false near infra red imagery?

Background : I use near infra-red imagery to delineate wetlands and water bodies with good success. It's also obvious to distinguish between new healthy vegetation and older growth and land areas with ...
5
votes
3answers
213 views

Colour matching satellite imagery from different time periods

Is it possible to colour match two separate satellite images taken at two different times? I am working with two high resolution, multispectral images that were taken approximately one year apart and ...
5
votes
2answers
556 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
1answer
131 views

Why does the peak of a mountain appear bright on Radar images

Why does the top of a mountain appear bright on a SAR (radar) image. I know that the peak of a mountain is subject to a layover effect, thus appearing closer on the radar image than the bottom part of ...
5
votes
3answers
61 views

Residential tree cover for surveying?

Can someone point me in the direction of some high spatial resolution and reasonably recent satellite imagery for central Canada (Manitoba)? I am trying to determine whether I can generate accurate ...
5
votes
1answer
107 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
625 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
5answers
6k 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 ...
4
votes
2answers
607 views

comparison of Historical aerial photographs to today's satellite images

I'm working on a project in which I have to compare vegetation cover changes. So we have 1950's aerial photographs which must be compared to actual satellite images. Images must be properly adapted ...
4
votes
1answer
235 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
170 views

Avoiding purple anomaly on imagery in ArcMap?

What is this purple anomaly 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 than that, I have not ...
4
votes
2answers
188 views

Download MODIS data for Mexico

I would like to download MODIS npp images for Mexico but I cannot figure out which files correspond to the country. How can I associate each tile to its location without looking at the million of ...
4
votes
2answers
519 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, ...
4
votes
1answer
455 views

Atmospheric Calibration for Landsat 7 ETM+ Gap Filling

This is for thesis work involving mapping of above-ground mangrove forest biomass using Landsat 7 ETM+ imagery. I am assessing correlations between biomass with vegetative indices, e.g. NDVI, and ...
4
votes
1answer
2k 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 ...