The links herein demonstrate an Infinite GridSM spread-sheet with A-L separate worksheets. The relationship between the spread-sheets is illustrated in the table below. This was the first spread-sheet built for Harris County, and is based around tieing the name of each Census Tract in the table (Worksheet B) to the location of that Census Tract (Worksheets C to K). Once each Census Tract on the table was cross-referenced with it's map location, it was a simple process to copy the cells to a composite worksheet (Worksheet L) and have the results input from the table mapped to the small maps, as well as the composite map. It was determined the Census Tracts could be mostly defined using an IG5 resolution. This is where each cell is 50" Longitude and 25" Latitude. A map was put together showing IG4 resolution across Harris County (Worksheet A). It takes a grid of 9 x 12, or 48 IG4 Grid Cells with a resolution of 7.5' x 3.75', to cover Harris County.
Note: Click on thumbnails for expanded image view
|Worksheet A: used to show Input values into an IG4 grid.||Worksheet I, NW Harris County||Worksheet J, CC Harris County||Worksheet K, NE Harris County|
|Worksheet B, Listing of Census Tracts in Harris County, used to input data to be mapped. Data could include opinion surveys, voting results, etc.||Worksheet F, CW Harris County||Worksheet G, CC Harris County||Worksheet H, CE Harris County||Worksheet L, Composite output map of Harris County|
|Worksheet C, SW Harris County||Worksheet D, SC Harris County||Worksheet E, SE Harris County|
Since this proof-of-concept sample is done with a simple Excel spread-sheet, there are limitations. If the results were database driven, it would be easy to bring results of polls and voting results and census data from the database tables directly to the map. Excell is limited to 256 columns, and so if you want to go to a very finer Infinite GridSM resolution, it is necessary to break the maps into pieces. It is a straightforward process to design a product based around this concept which will accept data from spread-sheets, SQL databases like Access and Oracle, or data manually entered.
All Texas Census Tract and Census Block maps are in standard formats. This means that it is a straightforward process to automatically generate grid cells at vaious resolutions, which are "mostly" over specific Census Tracts. Once this process is automated, the maps can be automatically updated everytime the Census Tract or Census Block maps are updated. These maps and grid cells can be automatically correlated against apprasial district maps, environmental maps, etc. One early result will be to identify discrepencies between maps generated by the various government mapping agencies. The gridding of the maps at various resolutions can be done from the original digital map data, or by taking the public domain pdf files and extracting the information from them.
However, before any of this can happen, and before Walden 3-D can proceed beyond this prototype, The Texas State Data Center must provide a letter to Walden 3-D giving permission to use copyrighted data.
To see how this initial work was expanded to work up and down Infinite GridSMscales go to http://www.walden3d.com/H/sample/CTmapCT
This page is at: http://www.walden3d.com/H/sample/CTmap/index.html