Hotspot Analysis with GeoMedia Grid. Shaun Falconer

Transcription

1 Hotspot Analysis with GeoMedia Grid Shaun Falconer

2 What is hot spot analysis? A method of detecting and presenting patterns in data Common approaches Point map Thematic map Density estimation map Sparse input Density Patterns Clusters Concentrations

3 Point Map

4 Thematic Map

5 Hotspots from Density map

6 Density (Hotspot) Maps We are looking at point source density hotspot

7 Alternative presentation of density: Isolines

8 Some examples Crime event analysis Asset or utility analysis e.g. outage location analysis e.g. repair analysis Epidemiological events (pandemic locations) Transportation events e.g. accident location analysis Earthquake events e.g. hotspot of earthquake by magnitude Bore hole samples by Magnesium level

9 GeoMedia Grid provides hotspot analysis GeoMedia Grid processes grid data using statistical and probability functions Provides functions targeted directly at point based hotspot analysis Local scan interpolation over sparse point data to produce density isopleth map bit like a DEM map Tools to process the density map, such as Hotspot extraction Isolines (like contours from DEM) Thematic of density map Input to further analysis, either grid or vector based

10 Where does Grid fit in with GeoMedia? GeoMedia is vector GeoMedia Grid is raster (cell, grid) They are integrated - Preliminary analysis typically undertaken in GeoMedia. E.g. source of data, aggregate or merge data, filter data, generate functional attributes - Rasterise to grid and identify hotspots - Within GeoMedia GWS environment and display - Vectorize the hotspots for further analysis, display or storage

11 A quick walk through

12 High level process Density Command Input: (Vector) point dataset of incidents Output: Density map Hotspot Detection Input: Density map Output: Hotspot map Vectorize hotspots Input: Hotspot map Output: Vector dataset of hotspots

13 Density Command 1. Use GeoMedia to identify Point dataset 2. Grid> Define New (study area) Define extents of area of interest Resolution (say 30m) 3. Grid> Interpolation> Density Select Point source identified in step 1. If available in dataset, set the Intensity Rest are pre-populated defaults

14 Density Command Density map will be shown in GeoMedia

15 Input to Density Command

16 (Optional) Thematic of Density Map Grid> Layer> View Legend Set precision: right click legend> Format Click Value then click Format Enter Decimal value (data dependent, e.g. 6), OK Set colour sequence: select all entries (use shift) Right click, colour sequence Choose start to end colours Choose path type Apply

17 Result: Thematic Density Map

18 Hotspot Detection Grid> Classification> Hotspot Detection Source: Density Map from previous step Multiple of Mean: data dependent. Try 5 OK

19 Result: Hotspot of density map

20 Finally: Vectorize hotspot map Grid> Layer> Vectorize to Feature Layer name: Hotspot output from previous step Conversion type: Area Output type: Partitioned Boundary Check Simplify output Confirm output feature class name

21 Result: Feature class that can be used in GeoMedia E.g. extract incidents within the hotspot for closer examination

22 Some theory

23 Adaptive bandwidth, kernel shapes and density Point B has neighbors closer to it than Point A, so the adaptive bandwidth for Point A is larger than that for Point B, since the adaptive bandwidth takes the average distance of the (in this case, 5) nearest neighbors of each point The volume of the kernel shapes needs to be equal

24 Results: Fixed bandwidth vs Adaptive bandwidth

25 Discrete Hotspot (The Process) Interpolation > Density Classification > Hotspot Detection X Y X Mean := Multiple of Mean Y

26 Where does GeoMedia Incident Analyst fit in? GeoMedia Incident Analyst is an extension that uses GeoMedia and GeoMedia Grid principally targeted at crime analysis workflows, that incorporates hotspot analysis in the workflow.

27 3D hotspot maps Thematic 3D maps further augments understanding of spatial phenomena GeoMedia Grid with GeoMedia 3D can be used to create 3D hotspot maps 3D thematic maps allow map readers to understand relationships within seemingly unconnected/unrelated data Webinar was held on 10 September look for recording shortly at webinars/archivedwebinars.aspx

28 Questions?