This brand new, online 6 week free MOOC (Massive Open Online Course) on Imagery starts on September 7th. If you’ve ever wanted more real world experience working with imagery, this MOOC is for you. Learn practical applications of imagery through hands … Continue reading
The Processing pane on the Image Analysis window contains various tools that can instantaneously process your data on-the-fly. However not all of the button are active all of the time. This is because each tool is dependent on the layers … Continue reading
There’s a lot of tiled imagery out there that gets delivered to people without any coordinates stored with the files. Often the coordinate information exists but it’s stored in a table. So how do you view it in ArcGIS. Continue reading
Imagery Analysts frequently have to measure features and determine their height. At ArcGIS 10.1, the Image Analysis window provides tools that give you the ability to take measurements of building heights directly from imagery. The process of making such measurements on imagery is referred to as mensuration. Mensuration tools apply geometric rules to find the length of lines, surface areas, or volumes using information obtained from lines and angles. Mensuration can include measuring the height and absolute location of features. Any georeferenced raster dataset can provide distance, area, point, and centroid location. Height measurements can be obtained when the sensor model is known. Sun angle information is required for measurements using shadows, while 3D measurements require a DEM.
This image shows how you could use the Base to Shadow tool to find the height of a building. The height is calculated by selecting a point at the base of the building and the corresponding point at the top of the shadow. For more information on the Mensuration tools and how to use them, see the ArcGIS Online Help.
Contributed by Natalie Campos.
By Rajinder Nagi, Esri Cartographic Product Engineer
In a previous blog entry, we discussed how you can use Landsat image services in ArcMap to see the change over time. In this blog entry, we dive further into Landsat image services and describe how you can create thematic land cover maps which can then be used for analyses, such as land cover change detection.
The image classification process involves conversion of multi-band raster imagery into a single-band raster with a number of categorical classes that relate to different types of land cover.
One question we hear a lot is “why does my high-resolution aerial imagery get downscaled when I add it into ArcScene?” The answer is that ArcScene automatically reduces all imagery resolution because ArcScene is memory-based and if your image is large (and exceeds available memory), ArcScene can become unresponsive. Think of the automatic downscaling as a self-defense mechanism.
So, while you can’t change the default resolution of the imagery as it’s added into ArcScene, you can adjust the image resolution using a quality control slider after it’s in your document. The quality slider is on the raster layer’s Layer Properties dialog, under the Rendering tab, and is titled “Quality enhancement for raster images”. Move it one step to the right and click OK. The image should improve. Navigate around and, if you’re still happy with performance, try another notch up.
If you reach ArcScene’s performance limit and the image quality STILL isn’t good enough for your needs, then you will need to clip out a new, raster image for your area of interest, and then repeat the process of finding the most appropriate display quality on the slider. You can also keep the larger, full extent image in the Scene document (with a lower resolution) for general background, if needed to provide context.
The trick is to adjust the slider one step at a time, until you find the optimum “display vs performance” setting that you are after for this particular doc. This value is hard to predict because it is also reliant upon what other layers are inside your ArcScene view. Also, because it’s difficult to test for contiguous chunks of available memory before attempting to allocate it, you should save your document often.