Lessons Learned Lab #7…

Sorry for the confusion in the lab today. Many lessons learned from Lab #7… and here they are:

  • One Project, One Projection. It’s always good practice to have all the shape files projected right and uniformly before adding them to the map canvas. That thought of “Oh I know this, I’ll project it later” is dangerous. Use “import” to avoid navigating down to the wrong (different) projections. Check the source panel and there should only be one projection, rather than many globe icons. (I got three today…)
  • Environment settings when using the Spatial Analyst extension. Two things to define in the environment settings: extent (a square bound) and mask (the actual study area, within the square, – similar to the clip feature, or “cookie cutter”, in clipping). Today I used the point file and had the mask wrong, so the Euclidean distance returned is weird pretty colorful dots, – because I defined the mask such that AcrGIS ¬†thought I’m only interested in the Euclidean distance at the points. Caution should be exercised when defining mask.


For this week’s lab assignment, please refer to the Lab #7 slides I just uploaded. It’s a graduated colored map showing the priority of public transit needs. The result returned after adding up the four parameter scores is a score ranging from 6 – 17, but we don’t want 12 categories of priority. We don’t really think the difference between score 14 and 15 is that significant, rather, we can categorize both 14 and 15 into “high”. So please reclassify the 12-category index again and have something more meaningful instead. For example, 3 classes (low, medium, high), or 5 classes (very low, low, medium, high, very high).

My apology again for the confusion. Looking forward to seeing your awesome maps!










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