In chats with Jason Grant and a few other architects, we've heard consistent questions that suggest that Project Galileo presents some concepts and tools that are unfamiliar to many architects. Here are some preliminary answers to a few of the most common questions that we seem to be getting:
Q: What is a shapefile and where do I get one?
A: A shapefile is a GIS file that started out as a proprietary format but which gradually became a defacto standard in the GIS industry. Think of a shapefile as a simple table that contains one column with a 2D graphic object and an arbitrary number of additional columns containing user-defined attributes that correspond to the shape. Each piece of data, or feature, in a shapefile is represented by one row or record in the table such that the record contains one graphic and the associated attributes. Shapefiles can be made by many types of GIS software, including AutoCAD Map 3D. Galileo can consume shapefiles containing points, polylines, or polygons and magically grow them into trees, rail lines, and buildings, for example.
(Note that this is a logical description of the shapefile. A full description of what is in a shapefile can be found in numerous sources online.)
Q: Where would a database file come from and how would it be used?
A: In the context of Galileo, a "database" typically refers to some kind of file or intranet-based source of data in a relational GIS structure. As described in the shapefile question above, this structure typically associates 2D graphics with attributes. GIS data in this format can be used for overlaying on terrain as "Coverages", buildings, roads, rail, city furniture, trees, water, and barriers. Database access is done through the open source Feature Data Objects (FDO) technology and the types of databases and database files that can be accessed is consistent with current releases of other Autodesk products that use FDO.
Q: How does a terrain surface file work with an image file and where would I find it?
A: There are many types of terrain surface files that may be used in Project Galileo. These files may be found in both vector and raster (image) formats. After a terrain file is brought into Project Galileo. There is a huge diversity of sources for terrain data and imagery, described reasonably well on wikipedia. The diversity in formats and resolution can be dizzying for GIS and non-GIS professionals alike. For really large areas, the US government publishes US and some world data online at their EarthExplorer site. Galileo uses an open source library for terrain called GDAL and should support most of the formats found on the GDAL raster formats site.
Q: How would a terrain texture file be used?
A: Terrain textures are most commonly aerial or satellite photographs of the ground and may be overlaid on a terrain to make the ground look more real. In the images from VTN Las Vegas on the Galileo Gallery, you can see that Keith Warren and his team have used aerial imagery to show streets, trees and other ground features in their models.
Typically terrain source files have intrinsic georeferencing. That is, the file contains some information that tells the software where on the globe it belongs. That is necessary because when you add other information, such as an aerial photo or a georeferenced building created in an Autodesk product, then the software can put the data together correctly. Image files usually do not have georeferencing inside the file. Instead for a TIF file, for example, you may find a TFW file next to it that looks like this:
0.125000
0.000000
0.000000
-0.125000
331473.140900
7394394.272800
While that is pretty meaningless to the human reader, this file defines the extent of the imagery data and where on the earth it belongs. If you have obtained terrain and imagery from a known source, such as your local city, then they typically will provide the 'world files' as these are called.
Q: Is a TIFF terrain the same thing as a TIFF image in Photoshop?
A: The GeoTIFF format that can be used for a terrain file is related to the TIFF that is thought of as an image file, however it contains additional information that encodes elevation information. While a GeoTIFF can be used as a terrain texture, a TIFF that is generated in Photoshop or another non-geospatial raster image editing application cannot be used as a terrain. The RemoteSensing.org site has some great information on GeoTIFFs.
Q: Which is the most efficient file format to import from for an Architect? (FBX, OBJ…)
A: There is no simple answer to this question today, unfortunately. FBX is a heterogeneous format that can differ subtly from implementation to implementation. OBJ tends to be very large. For simple models, we have had success with OBJ. For Revit models, we have had more success with FBX exported from 2011 Revit and LandXplorer, but we're working on consistency issues.
We'll hopefully have more tips on this soon.
Q: What is LandXML data and where does it come from?
A: LandXML is an open standard for exchanging civil drafting information for terrain surfaces and other terrain-related objects. We currently use LandXML as the exchange format to receive information in Project Galileo from AutoCAD Civil 3D. If you are working on a project that includes some recently graded sites or cuts for road ways or utilities trenches, then it's possible that the civil engineer you work with can provide exports from their model in LandXML format.
Q: What are coordinate systems and which should be used?
Short A: You're an architect with no interest in GIS concepts. You simply want to use some cool data like terrains, imagery, building footprints, streets, and trees to make a really cool context for a detailed project you are working with. My advice... work with someone familiar with GIS to get you a package of the data you need which should all come with the right 'world files' so that Galileo recognizes them and you can ignore the need to set the coordinate system. And make sure that they tell you what coordinate system it was.
Warning: It may cost you. Good data is rarely free.
Another warning: If you don't know the right coordinate system for some GIS data you found and you just pick one, data import may fail. Not all coordinate systems are created equal. Some are quite a bit more equal than others.
Long A: Everything on the earth has a location or coordinate. We collect those locations in both 2D (latitude and longitude or X and Y) and 3D (add altitude or Z). You, as a user, want to take real world objects with real location information and and use them in a 2D or 3D scene, preserving their exact location, orientation, and shape. But how do I take a civil terrain, a 3D model, a terrain file, and a bunch of 2D tree locations and get them to match up to be in the right place in the scene?
The only way to do this is if I know the right coordinate system and datum for the objects. A coordinate system can be thought of as the units and location of the XYZ origin axis for the scene. Different coordinate systems are used to optimize accuracy in shape, distance, and position on the earth depending on the area of the project that you care about. A datum is essentially a model of the curvature of the earth. Different data are created using different curvature models, such as models that are developed at different times or models that are developed to maximize accuracy for different parts of the globe.
In most cases, you'll likely be working with some kind of local coordinate system that best represents the region where you are working. If your local government provides data for free online, they will typically advertise the coordinate system in which they stored their data. The Marin County data repository posts this statement:
All GIS data are in California State Plane coordinates, NAD83, HARN in US Survey feet.
That way, if for some reason a file that I get from MarinMap.org doesn't open with the coordinate system predefined, I can search through the coordinate system picker and find the correct entry. Galileo attempts to remember the last used system to make it easier to find the next time.
If you're really curious, there's a ton of literature out there on coordinate systems, projections, and datums. You can start with wikipedia and procrastinate successfully for several days by following some simple Google searches.
I recognize that some of these answers don't go far enough, but there are several PhD's worth of questions here. As we discover specific scenarios that can help you understand some of these concepts, we'll try to share them on the blog.