The City of Philadelphia funded watershed-scale color orthophotography for all the City's watersheds, including Wissahickon Creek Watershed. An orthophotograph is digitally processed to make the photograph accurately represent features on the ground despite elevation differences and the fact that individual photographs are taken from different locations and lenses will introduce perspective-related errors. Much of this data is presently available for download from Penn State University's Pennsylvania Spatial Data Access website (PASDA), search for "ortho". Download Area 9 (MrSID image), available on this data DVD-ROM.

Users in Springfield and Whitemarsh Township would also need to download Area 5

USGS 7.5 minute topographic maps, or "topos" are probably the most familiar topographic maps. The maps combine the natural contour features with man made structures and are still commonly used for navigation, with or without assistance from a GPS. These maps have been digitized and "georeferenced", meaning that they will be displayed in the correct location when opened with GIS software. The table below has a key to which topo maps are needed for which of the project areas.

Index

Ambler Quad

Germantown Quad

Lansdale Quad

Norristown Quad

NOTE: Letters indicate geographic coverage E = Entire M = Most area P = Partial Area

USGS 3.75 minute Digital Orthophoto Images (AKA DOQQs or "Quarter Quads") are available from the USGS. As the name implies, these maps split a USGS quadrangle into four images at 1 meter resolution. These images are greyscale and originate from 1996. One interesting application of these images is to overlay the DOQQ with a more recent aerial photograph and look for changes, such as construction or changes to a stream's geometry. These maps have been digitized and "georeferenced", meaning that they will be displayed in the correct location when opened with GIS software. The following is a key to which DOQQs are needed for which of the project areas.

Lower Gwynedd Township: Lansdale NE Lansdale SE Ambler NW Ambler SW

Montgomery Township: Lansdale NE Ambler NW

North Wales Borough: Lansdale NE

Springfield Township: Germantown NW Germantown NE also small polygon in Ambler SW

Upper Dublin Township: Germantown NE Ambler SE Ambler SW

Upper Gwynedd Township: Lansdale NE also small polygons in Ambler NW, and Lansdale SE

Whitemarsh Township: Germantown NW Norristown NE Lansdale SE Ambler SW

Whitpain Township: Lansdale SE Ambler SW

PWD GIS analysts and co-op students from Drexel University painstakingly traced hydrographic features of Wissahickon Creek Watershed, based upon 2004 Color Orthophotography. Data are available as polygons, in which the entire stream was digitized from bank to bank, as well as a centerline layer where the line was traced along the center of the stream.

Download the Hydrology Lines Layer

Download the Hydrology Polygons Layer

Municipal Boundaries were useful for determining which municipality certain features, such as stormwater basins or infrastructure features were in.

Download the Municipal Boundaries Layer

This basemap roads layer is poorly documented and is of questionable accuracy but has been included because there are few sources of this information. Layers provided by PennDOT available on PASDA do not include the road name, making them less useful for map making purposes. The user is encouraged to check back often or explore other sources for this information. Roads information is readily available with various free online mapping services.

Download the Roads Layer