Lab 4 - Ground Truthing and Accuracy Assessment

In this lab, we investigated our LULC map from last week to assess our classification schemes and determine our skills of aerial photo interpretation. As we obviously could not visit Pascagoula, Mississippi to actually verify our classification, so we used Google Maps instead. I created a new shapefile for which there are fields for the old classification, the new classification, and whether or not they match. I used the Editor tool to create 30 new points, relatively evenly spaced throughout the map and ensuring there was at least one point for every classification type. Then I used Google Maps zoom feature and the Street View feature to match the location of my points to Google Maps in order to confirm the actual land use/land cover classification type. Once I did this, I calculated the percent of sample points that are correct. To calculate the accuracy, I divided the # of correct points by the total # of points and multiplied by 100 to get an accuracy percent. In this case, the original land use/land cover classification scheme is 53% accurate. The new map is shown below. The green points are those correctly classified in the original scheme and the red points were those incorrectly classified. The original classification was performed using only aerial imagery, so distinguishing between similar classification type proved especially difficult (i.e. deciduous vs. evergreen forest or commercial vs. industrial buildings), and this seems to be where most of the inaccuracies were.