GEOG 379 Lecture Notes - Lecture 13: Image Analysis, Web Mapping
27 Apr 2018
School
Department
Course
Professor
4/11 – GIS Problem Solving and Change Detection
Change Detection in GIS
Coeptualizig Chage i “pae
• Change in location
o Tracking path of a feature
o Change in distribution of features w/in an area
• Change in character
o Land use, land cover, or environmental data
• Change in magnitude
o Change in population or area
Approaches for Measuring Change
• Absolute change
o Absolute growth or decline
• Percentage change
o Normalizing data
o (Valuei + x – Valuei) / Valuei * 100
• Categorical change
o Overall change in w/in a category or b/w categories
o Can be reported in absolute or % terms
Considerations When Measuring Change
• Consistency of data collection + classification procedures
o Data sources + collection methods
o Classification methods
• Spatial consistency
• Attribute consistency
Why Worry About Spatial Consistency?
• Boundaries can change over time + complicate temporal comparisons
o Annexation can change municipal boundaries
o Census Bureau changes boundaries used to collect + report data
• We have data at one level of aggregation that we want to use at another
o Population living in the service area or buffer of certain facility
Options for Dealing with Changing Spatial Units
• Option 1 – only estimate change where geographic areas are (usually) consistent
o Changes at county level are rare
o This ist addressig prole of hages i geography, its just avoidig it
• Option 2 – assume an even spatial distribution thru out that area in the earlier time period
o May be reasonable for the edges of cities (where farmland has turned into a
subdivision)
find more resources at oneclass.com
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Document Summary
4/11 gis problem solving and change detection. Co(cid:374)(cid:272)eptualizi(cid:374)g (cid:858)cha(cid:374)ge(cid:859) i(cid:374) pa(cid:272)e: change in location, tracking path of a feature, change in distribution of features w/in an area, change in character, land use, land cover, or environmental data, change in magnitude, change in population or area. Considerations when measuring change: consistency of data collection + classification procedures, data sources + collection methods, classification methods, spatial consistency, attribute consistency. Location of houses from 911 addressing data: geocoded locations of utility customers. Change detection from raster data: widely used for change detection of land cover and vegetation, mostly use satellite imagery, may require more idea on remote sensing and image analysis. Step 2 methodological design: the core of a gis project. Is it technically feasible: what techniques/methods do we have, draw the detail outline, revisit research questions if necessary. Does the result look alright: go for ground truthing if necessary, share with colleagues for review.
