Export Basemap Imagery from GIS to CAD

Transcription

1 Export Basemap Imagery from GIS to CAD This tutorial illustrates how to add high resolution imagery as a basemap into an existing CAD drawing using ArcGIS and AutoCAD. Through this method, the imagery will be correctly scaled and georeferenced without the need to manually place or scale the imagery by hand. By using high resolution imagery, this method will be suitable for large format printing. This tutorial uses ESRI ArcGIS 10.2 and AutoDesk AutoCAD 2014, and would require a familiarity with this software to complete. Help is available, for more info on access to the software and help with the procedures visit This tutorial is part of a series: 1. Finding GIS data on the web 2. Finding and preparing elevation data for contours 3. Finding and preparing aerial imagery for basemaps Converting between GIS, CAD and other formats: 4. Exporting vector data from GIS to CAD 5. Exporting contours from GIS to CAD 6. Exporting Imagery from GIS to CAD 7. Exporting 3D Buildings form GIS to Rhino The General Approach Preliminary steps: 1. Begin with an ArcMap document and GIS data in known, projected coordinate system. In this example, data from Santa Barbara county is referenced in the Coordinate System: NAD 1983 State Plane Zone V feet 2. GIS shapefile layers were exported to a CAD.DWG file in a previous tutorial. In ArcMap: 1. In the ArcMap document, Add Imagery to the map 2. Set page layout to desired final page dimensions (eg 36 x 48 ) 3. Set the map scale to suitable value (eg 1:600, aka 1 = 50 ) 4. Record XY Coordinates for the bottom left corner of the image 5. Export Map as a.jpg image (300 dpi) In AutoCAD 1. Open existing CAD.DWG file, one with the same, known coordinates 2. Attach Image 3. Set image Scale and insertion point, (this is known from the values recorded earlier). 4. Change image layer drawing order or transparency as needed.

2 Exporting Imagery from GIS to CAD 1. Open ArcMap, zoom to project location. 2. Add your existing aerial imagery. Sources of imagery may be: City or County aerial imagery available on your local GIS file server, Publicly available imagery accessed through a GIS server (for example, you can connect to 1m resolution 2012 NAIP Imagery using California Fish and Wildlife Map Services), Image files downloaded from mapping agencies. For example, 1 ft. resolution aerial imagery for most urban areas can be downloaded as GeoTiffs through the USGS National Map. 3. With the imagery added, zoom and compose around project location. 4. Go to Layout View, and change layout to desired final page size. What is the final print size needed for the project? eg 36 x 48 Landscape?

3 5. Extend the Data Frame to fill the full extent of the map document: View Data Frame Properties, and on the Size and Position tab, Set Position X and Y to 0 and 0; Set Width and Height to 48 x 36. This will set the data frame to the entire page, and makes the final image borderless (with no surrounding white space). 6. Set Map Scale to desired scale, ideally, some even scale. Note this map scale, you will refer to it later. In this case, scale is set to 1:600.

4 You ll need to record some more information about the imagery to ensure that the image can be correctly georeferecend and scaled in AutoCAD. 5a. First, you need to know\verify the coordinate system of your existing GIS data. In this case, the vector data is referenced to the coordinate system: NAD 1983 State Plane Zone V feet. Knowing this, you will need to set\verify that the Coordinate System of the Data Frame matches your existing data. View Data Frame Properties Coordinate System: Projected Coordinate System State Plane NAD 83 (US Feet), that is NAD_1983_StatePlane_California_V_FIPS_0405_Feet

5 5b. Now, obtain the image Extent Coordinates in ArcMap: View Data Frame Properties Data Frame Choose Fixed Extent from the drop-down list. Copy and Paste the Left and Bottom coordinates into a.txt doc or spreadsheet. These are the X,Y values for the lower left corner of the image.

6 7. Export the image from ArcMap using File Export Map. Turn off any other layers, except the imagery you want to be displayed. Save Image as JPG at 300 dpi. On the Format Tab, choose JPEG Quality 85 (this will help to reduce the large file size of the image). For example, a TIFF image at this size would be over 450 Mb while a JPG 7 Mb with little, if any difference in image quality. Save imagery to the same folder location as your CAD document, these files need to stay together.

7 In AutoCAD 2014, open your existing DWG 8. By Default, the image will be added to the Active Layer. Create a new layer blank layer named Basemap Imagery and set that as the active layer Insert Attach and browse to choose your image.

8 Insertion Point and Scale 9. Here you will specify two items, the insertion point and the scale. These refer to the, the location of the lower left corner of the image, and the scale factor (described more below). For the Insertion point, Use the X, Y coordinates for Left, and Bottom you recorded earlier. Note, omit the comma separators when entering coordinates into AutoCAD. To correctly set the scale of the image, you will need to know: 1) Map Scale of the image exported from ArcMap: 1:600 or, 1 = 50 2) Units of the AutoCAD document: units are feet. 3) Units of the image itself units are inches AutoCAD is asking; 1 unit of the image corresponds to how many map units of the AutoCAD document? Given an image with a map scale of 1:600, one inch of the image corresponds to 50 ft.: So the Scale factor here is iiii 1ffff xx = 50 ffff. 1iiii 12iiii

9 Robert E. Kennedy Library Data Services When placed, this high resolution image will be inserted into AutoCAD at correct location and scale. This can serve as a valuable basemap and will support large format printing at 36 x 48 at 300 dpi. 10. Change Drawing Order to place imagery behind or under the vector layers. Command DrawOrder Select image Object B for Behind all

10 11. For Transparency Select Image Image Fade enter amount.

11 The final output can be a high resolution PDF, with both CAD and imagery blended. 1. Note, upon opening the exported DWG file, AutoCAD may show an Error: In these cases, AutoCAD will continue to open, and the DWG file can open properly from within AutoCAD. File Open Drawing.

12 Some follow-up notes about saving your CAD and imagery files. When the imagery is attached to the DWG, it is not saved within the CAD document, the imagery is still stored in the separate jpg file from where the file was attached. If you need to move or send your CAD document, be sure to include both the DWG and image file, and keep them in the same folder (the same relative position, in terms of folder structure).

13 Alternatives Of course, this is not the only way to achieve these results, and there are some alternative steps in this procedure as well. Some examples include: 1. AutoCAD Civil 3D or Map 3D While on its own AutoCAD 2014 does not directly read georeferenced imagery, AutoCAD Civil 3D or Map 3D can. If these programs are available, geotiff images that downloaded from the USGS National Map or exported from ArcMap could be read into either Civil 3D or Map 3D and exported as a DWG file, and then read in AutoCAD See online tutorial here from MasterGraphics. 2. Add imagery through AutoDesk Live Maps In AutoCAD 2014, it s possible to connect directly to aerial imagery and other basemaps from Microsoft Bing Maps, all from within AutoCAD. See this video tutorial for a demo. Unfortunately, imagery accessed this way is available for viewing only; it s not possible to use this imagery in layouts or for high resolution prints. 3. Connect using ArcGIS for AutoCAD ESRI s ArcGIS for AutoCAD is a free plug-in for AutoCAD that can be used to view ESRI Imagery, Basemaps, and other GIS data from ArcGIS Online or ArcGIS Server. This approach can provide the benefits of viewing, Enterprise GIS data in the CAD environment. Again, however, imagery served through ArcGIS for AutoCAD is only available for viewing, and neither layouts nor high-resolution exports are possible. 4. Finally, for alternative GIS software there s QGIS The procedure outlined in this tutorial for exporting imagery with known scale and coordinates can also be done using the free and open source QGIS program. The menus may be different, but the same general procedure would apply.