Download Contour Lines as DXF for AutoCAD and Civil 3D

Generate contour lines for any site in Oregon from USGS 3DEP lidar elevation data, and download them as a DXF that opens at true scale, in feet, in AutoCAD, Civil 3D and other CAD software.

What is DXF?

DXF (Drawing Exchange Format) is Autodesk’s open format for moving drawings between CAD programs. It has been around since the early days of AutoCAD, and almost every CAD, survey and civil design package reads it.

For contours, DXF has one big advantage: each contour can be stored as a 3D polyline that sits at its real elevation, so the height is read straight from the Z coordinate. CAD software can build a terrain surface from the lines without anyone typing in elevations by hand.

What you get in the file

• 3D polylines: each contour is a 3D POLYLINE with its elevation as Z on every vertex. Closed loops (hilltops, hollows) are flagged as closed.
• Feet throughout: X, Y and Z are all in feet, and the drawing units are set to feet.
• Projected coordinates: coordinates are projected to Oregon Statewide Lambert, feet (EPSG:2992) and shifted to a local origin near your site.
• Origin in the header: a comment at the top of the file gives the origin’s easting and northing, so you can move the drawing back to full coordinates.
• One layer per elevation: layers are named CONTOUR_<feet>, such as CONTOUR_400, so index contours are easy to pick out.
• Source credit: header comments name the USGS 3D Elevation Program and its public-domain status, so the source travels with the drawing.

Software that reads DXF

CAD

• AutoCAD and AutoCAD Map 3D: open DXF directly.
• Civil 3D: use the polylines as contour data for an existing-ground surface.
• BricsCAD, DraftSight and MicroStation: read and write DXF.
• SketchUp Pro: imports DXF; the Sandbox tools can make a terrain surface from the contours.
• Revit and ArchiCAD: can import DXF as a base for site modeling.

Survey and civil design

Survey and civil packages such as Carlson, Trimble Business Center and Bentley OpenRoads generally import DXF linework with elevations. The import steps differ from version to version, so check your software’s documentation.

GIS

• QGIS: opens DXF as a vector layer. Set the layer to EPSG:2992 and remember the local origin.
• ArcGIS Pro: reads DXF as a CAD dataset.

For GIS work it is usually simpler to download contours as GeoJSON or a Shapefile instead.

How to download contour lines as DXF

1. Open the map: go to Download Data and search for the address or place.
2. Select the area: draw a rectangle around the site, or click a taxlot to select the rectangle around it. The area can be up to 7.5 miles per side.
3. Choose the interval in feet (1, 2, 5, 10, 20, 40, 100, 200, 500 ft) to suit the drawing scale:
   • 1–2 ft: site plans at 1″ = 20′ to 1″ = 50′, house pads, driveways and grading
   • 5 ft: lot and subdivision layouts at around 1″ = 100′
   • 10–20 ft: larger parcels, rural acreage and early feasibility studies
   • 40 ft and up: big, steep areas such as the slopes of Mount Hood or the Coast Range
4. Choose DXF among the contour formats.
5. Download: the contours are free to view on the map; the file itself needs a pass.
6. Insert into AutoCAD: open the file, or bring it into your drawing with INSERT or as an XREF.

Using DXF contours in AutoCAD and Civil 3D

1. Insert: open the DXF, or attach it as a block or XREF in an existing drawing.
2. Place it: to work in full EPSG:2992 coordinates, move everything from 0,0 by the origin’s easting and northing given in the file.
3. Layers: every elevation already has its own CONTOUR_ layer; group every fifth one as index contours.
4. Lineweights: give index contours a heavier line than intermediates so the plan reads at a glance.
5. Labels: add elevation labels along the contours where the sheet needs them.
6. Surface in Civil 3D: add the polylines to a TIN surface as contour data for profiles, sections and volumes.

Common uses

Site planning and new homes

Architects and designers use the contours as the base for site plans: placing the house, garage and driveway, and seeing how the ground falls toward neighbors and the street. See also: Property contour map for an Oregon taxlot.

Building permits and land-use applications

Site plans and sections often need to show existing grade. Lidar contours are a solid starting point, but the county or city decides what it accepts, and it may ask for surveyed elevations where levels are critical. Check with your county planning department. See also the slope map for building permits guide.

Earthwork and access roads

Contractors use the contours to rough out earthwork, plan access roads on steep ground in the Coast Range or the Cascades foothills, and set up a preliminary terrain model before detailed survey. For a quick cut and fill figure, try the Cut & Fill tool directly on the map.

Landscape architecture

Terraces, walls, paths and stormwater features all have to work with the ground. Contours show where levels fit naturally and where water will run.

Survey background

Surveyors use lidar contours as background between surveyed points, especially on large or hard-to-reach parcels.

Tips

Match the interval to the scale

A 1″ = 20′ site plan can carry 1 ft contours; a sheet covering a whole ranch in the Willamette Valley foothills is unreadable with anything closer than 10 or 20 ft. Finer intervals also make bigger files.

Keep large areas light

Large areas at fine intervals produce heavy drawings. Attach the contours as an XREF to keep the main drawing fast. Output resolution scales with the size of the area you select. Exports are capped at 1,024 pixels on the longest side, with a floor of 3.3 ft per pixel — so a 900 ft building site is delivered at the full lidar detail, while a block 7.5 miles on a side is resampled to roughly 39 ft per pixel. Select a smaller area when you need fine detail.

Bare earth, not buildings

Contours come from the bare-earth elevation model, which shows the ground without buildings or trees. That is what you want for terrain contours, but it means houses and canopy do not appear in the file.

Fine intervals need lidar

Where no full-resolution lidar exists, the source falls back to a coarser model of about 33 ft per pixel. Contours finer than about 20 ft over that model show noise rather than real terrain.

DXF or another format?

DXF or GeoJSON

DXF is built for drafting and design. GeoJSON suits GIS and web maps, in WGS84 with the elevation in feet on every line.

DXF or Shapefile

A Shapefile carries the elevation in an attribute table and fits traditional ArcGIS workflows. DXF is the better choice when the contours go into a CAD drawing.

DXF or PDF

PDF is for viewing and printing, DXF for editing. Download contours as PDF when you need to share a map with someone who does not have CAD.

About the data

Ground elevations on this site come from the USGS 3D Elevation Program (3DEP) seamless bare-earth model: 3.3 ft per pixel where lidar has been flown and about 33 ft per pixel elsewhere, with elevations above NAVD 88. The data is in the public domain. Most of Oregon’s lidar was flown through the Oregon Lidar Consortium, run by DOGAMI, the Oregon Department of Geology and Mineral Industries. DOGAMI reports about 99% of Oregon covered by at least one lidar project. See lidar coverage in Oregon for the project behind your area. More from the USGS 3D Elevation Program and DOGAMI’s lidar program.

Accuracy is inherited from the USGS 3DEP source and the lidar project behind it, not asserted by this tool. Where lidar exists, at 3.3 ft per pixel, vertical accuracy is that of the project: individual Oregon Lidar Consortium projects report vendor RMSE of a few inches or less in DOGAMI’s project records; for example, Metro 2014 reports about a tenth of a foot. Outside the lidar work units the seamless DEM is about 33 ft per pixel and far coarser. Every download states what share of its area fell outside the lidar work units. Values are bare-earth elevations above NAVD 88 from a digital elevation model — they exclude buildings and tree canopy and are not a substitute for a surveyed elevation where a legal or engineering decision depends on it.

Frequently asked questions

Other formats

• Contours as GeoJSON – for QGIS and GIS
• Contours as PDF – for printing
• Contours as KML – for Google Earth
• Terrain as STL – for 3D printing
• Contour lines for Oregon – overview of every format