First Floor Elevation Mapping
Mississippi-Alabama Sea Grant, in cooperation with Gulf of Mexico Alliance Community of Practice, funded an innovative project to overlay building first-floor elevations on top of U-Surge flood levels to assess flood risk in Galveston, Texas. This project pioneered an effort to use Google Street View and Google Earth for first-floor elevation mapping.
This pilot project provides an innovative, data-driven approach that can be followed by other communities. The optimal methodology for generating first-floor elevation data was refined through the project, with many lessons learned. The marked-up photos used to document this process, originally included as "Appendix B" in the project report, became so numerous that the size of the report became cumbersome.
Therefore, we have uploaded this appendix to this website, as it serves to provide guidance for other communities generating first-floor elevation maps of their own. As the outreach from this project expands, we will link any Sea Grant pages that relate to this project. Thank you, Sea Grant, for funding such an innovative project! Funding for the pilot project was given from Mississippi-Alabama Sea Grant to Galveston Historical Foundation.
This pilot project provides an innovative, data-driven approach that can be followed by other communities. The optimal methodology for generating first-floor elevation data was refined through the project, with many lessons learned. The marked-up photos used to document this process, originally included as "Appendix B" in the project report, became so numerous that the size of the report became cumbersome.
Therefore, we have uploaded this appendix to this website, as it serves to provide guidance for other communities generating first-floor elevation maps of their own. As the outreach from this project expands, we will link any Sea Grant pages that relate to this project. Thank you, Sea Grant, for funding such an innovative project! Funding for the pilot project was given from Mississippi-Alabama Sea Grant to Galveston Historical Foundation.
Example 1A
Measuring vertical and horizontal pixels on Google Street View (in Google Earth)
Example 1B
Measuring roof edge on Google Earth aerial photo (top down)
Example 2
Measuring vertical and horizontal pixels on Google Street View (in Google Earth).
Note: In some cases, the main house roof is measured - not the porch roof
Note: In some cases, the main house roof is measured - not the porch roof
Example 3
Elevation view is obstructed
Example 4
The elevation view becomes visible when the camera is moved down the street. Some notes about this:
1. Notice that the camera points perpendicular to the edge of the street. Therefore, the target house is not in front of the camera, but offset to the side.
2. Notice that the entire roof edge, from left to right is not visible, because the right edge is cut off. To improvise, measure the shorter distance, from left edge of roof to the point that this roof edge meets the front porch roof.
3. Note that the left roof edge is not actually visible, because the telephone poll blocks it. However, in this case, we can estimate the location of roof edge based on intersection of two roof planes.
1. Notice that the camera points perpendicular to the edge of the street. Therefore, the target house is not in front of the camera, but offset to the side.
2. Notice that the entire roof edge, from left to right is not visible, because the right edge is cut off. To improvise, measure the shorter distance, from left edge of roof to the point that this roof edge meets the front porch roof.
3. Note that the left roof edge is not actually visible, because the telephone poll blocks it. However, in this case, we can estimate the location of roof edge based on intersection of two roof planes.
Example 5
Counting stairs on Google Street View (in Google Earth)
Example 6
Trees obstruct the view of the roof, so it is not possible to calibrate elevation estimate. So this record is canceled in the database and the color turned to grey.
Example 7
Trees obstruct roof and shrubs obstruct elevation. It is not possible to calibrate the elevation measurement, so this event is canceled in the database and is shaded grey.
Example 8A
Example 8B
Example 9
Example 10
This is a garage. Enter "0" for elevation and mention in the notes that this is "slab on grade".
Example 11
Example 12
Example 13A
Example 13B
Example 14
Example 15A
Example 15B
