2018 Contours

2-foot contours derived from 2018 elevation data

Links

Download Shapefile

Due to the size of the dataset, it will not be provided as a GeoJSON. We also do not have any operational use for a contour Feature Service, so no live service link exists.

There is a vector tile layer open to the public, which can be added to the major desktop GIS softwares and web platforms.

Layer Information

Source

This layer was derived from elevation data obtained from the Illinois GeoSpatial Data Clearinghouse. Full metadata on the raw data is available there.

Processing

Using the above-referenced data, we used the Geospatial Data Abstraction Library’s gdal_contour tool to generate 2-foot contour lines.

We then used field calculations to identify individual contour lines as index lines (multiples of 10), storing that attribute in its own field.

Due to the level of detail of the input data, the output included tens of thousands of tiny contour loops, especially in relatively flat areas. We selected closed loop contours measuring less than 30 feet in length and removed them from the dataset.

Fields

Field	Description
ELEV	Elevation value of the countour
index_line	0 for standard contours, 1 for index lines