14GroundTruthingandAccuracyAssessLectureNotes - 1 Unit 14...

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1 Unit 14 Ground Truthing and Accuracy Assessment Accuracy assessment determines the usefulness of a particular digital image product, usually a land-use land-cover map. Accuracy assessment affect the legal standing of digital mapping in the courtroom. So far, there has been relatively little comparative research on the accuracy of particular techniques compared to others. There are two main phases to accuracy assessment. Ground Truthing is the phase where the study area is visited in the field, and examined to see if the classes shown on the map are correct. Accuracy assessment is the phase where the data collected in the field is compared to the data shown on the map, and an analysis of the structure and causes of errors is undertaken. As we discussed in the image enhancement section of this course, most people form opinions based on the appearance of a map. The pretty picture qualities are important: the map must be aesthetically pleasing, with a reasonable color scheme, patterns and shapes that make sense. Usually this works to the image analysts favor. In the courtroom, the opposite is true. People generally have faith in maps and data sources like the census, but they have problems understanding digital image analysis, especially since it can be shown that the images are nothing but little squares of colors. On the other hand, juries find aerial photographs convincing and easily understood. In fact, aerial photographs are more convincing than maps. A good digital map, made from recent data, is better than a topographic map for many purposes because it shows all land-covers from which land-use can be interpreted. Furthermore, we can make use of the biophysical information that exists on imagery which is unavailable on topographic maps. Both India and China have more or less decided to build their national map data base from satellite imagery rather than from traditional surveying sources. The strength of any digital map is the ground truthing and accuracy assessment that has been made. The weakness of a digital map are the flaws in the accuracy assessment strategy. in the best of all possible worlds, we would always design a remote sensing project with the accuracy assessment phase as the highest priority. Therefore, ground truthing and accuracy assessment must be considered in the design phase of any project. Accuracy Assessment in the Design Phase of the Project Generally speaking, you can assume that ground truthing will take up 60% of a projects time in person/hours and an even larger share of the project budget. The steps to consider in the design phase are: - Identify goals of project - Formulate hypothesis - Data Acquisition * What is needed for analysis
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2 * What is needed for ground truthing and accuracy assessment ancillary data: imported from GIS or databases, aerial photographs: to help with ground truthing and accuracy assessment ground survey designed for accuracy assessment We will look at these last two in some detail. Ancillary Data
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This note was uploaded on 12/21/2010 for the course GIS 4037c taught by Professor Roberts during the Fall '10 term at FAU.

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14GroundTruthingandAccuracyAssessLectureNotes - 1 Unit 14...

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