HLS 6070 DF4 Assignment Comments Part 1: GIS Software

Comment on these 2 postings as if you were talking in my voice, do not lose the name above each post. 100 words and 3 sources each:
Tyler Cuming: 
As a non-technical person myself, I find this a little difficult, but If I were a GIS operator briefing Image Rectification and Conversion to Radiance to non-technical executives, I’d try to break down the process in the simplest terms possible.
First, I would explain that image rectification is when you change an image from a file coordinate system to a map coordinate system. There are a number of map systems available for different scenario’s, which is why there are both file and map coordinate systems. A map coordinate system is the everyday map that we are all used to with x and y coordinates. The file coordinate system would be an image from say a satellite or a plane. If you want these images to be given coordinates on a topographical map, they need to be given earth coordinates, which differ from the ones they are given in their file image format. To do this, the best way is to find a “control point” on an x/y map such as a key terrain feature (e.g road, stream). Once you get multiple control points, you can overlap the images to create a common plane.
Radiance is electromagnetic energy measured in units such as watts. The reason that this is done in GIS is because by looking at the amounts of radiance on the earth’s surface, you can tell how much a certain area has changed over time. During the process of conversion to radiance, you can also see unique characteristics of the earth’s surface and other patterns from quantitative remote sensing. These conversions are done using algebraic algorithms, but are nonetheless very important to GIS.
Susan Schiller:
Image rectification is the process of adjusting the shape, size and orientation of an image so that it displays to scale across disparate map projections. In layman’s terms, standard image projection is analogous to transliteration whereas image rectification is analogous to translation. This is important so that the image can be understood in context with the projections and GIS layers for which it is embedded.
Conversion to radiance is the mathematical process of taking an image and determining EM reflectance based on the amount of light or “brightness” (Lawrence Fox III, 2015) of each individual pixel in that image. In layman’s terms it’s the ability to calculate electromagnetic reflectance based on the sum of the image’s parts. This is important because identical images taken over time can be deconstructed to yield valuable information about topographical changes.
Susan
Works Cited
Lawrence Fox III. (2015). Essential Earth Imaging for GIS. Redlands: ESRI Press.