This is a guest post by Michele Mattix of Geomattix, LLC. Michele is the excellent author of several e-learning courses that we sell including: GPS Mapping with ArcPad, Integrating GPS Data with GIS, Introduction to GPS Technology, Adding Digital Photos to GIS, Working with Coordinate Systems in GIS and GPS, GPS Mapping with Trimble’s TerraSync and Pathfinder Office, and the GPS Bundle.
CAD users beware! While ArcGIS supports the mapping of CAD data, ArcPad – ESRI’s field software – does not. Though it is no problem to convert CAD data into the geodatabase format, the handling of CAD annotation can present challenges. In this article, I will walk you through a problem one of my clients was having and the solution I came up with.
My client has a Trimble GeoXH GPS unit on which they use ArcPad to collect field data. I was contacted to help them clean up their GIS data. In addition to maintaining GIS data, they also had several CAD files. They wanted to consolidate all of the data into one efficient geodatabase. I designed and created a new geodatabase for them and converted/imported the CAD data into it. Among the CAD data were very detailed roads data that my client wanted to use as background data in ArcPad. In CAD format, the roads were stored as lines and the road names were stored in a CAD annotation feature class. When I converted the CAD data into the geodatabase format, two feature classes were created: Roads – which contains the line data, and Roads_Annotation – a point feature class that contains the road names. See the figure below.
When viewed in ArcMap, the raw CAD Polyline (roads) and Annotation layers appear as roads with labels, see below. My client wanted to reproduce this same look with the geodatabase data.
Using the newly created geodatabase Roads_Annotation layer – which contains point data with road names as attributes — overwhelms the map with unnecessary points. Also, the labels will not necessarily be oriented along the roads, as show below.
It would be nice to use the road names from the Roads_Annotation layer as labels in the Roads layer. I could accomplish this by joining the two tables if only there were a key field. Alas, there is not.
There is an Import CAD Annotation tool available in ArcToolbox that will convert a CAD annotation feature class into a geodatabase annotation feature class. The annotation will look exactly as it does in the raw CAD data. I used this tool to create the Annotation_rds feature class that works great in ArcMap. ArcPad, however, does not support annotation feature classes.
My client wanted both the roads and the road names to appear in ArcPad. With no other options, I needed to find a way to use the Roads_Annotation point feature class to label the roads properly.
Here’s how I made the Roads_Annotation point layer mimic the raw CAD annotation. First, I symbolized the points so that they do not appear on the map. I did this by choosing a basic ESRI point symbol that does not contain an outline, such as Circle 1, and then shrinking the size down to 7 points – any small size will work. In the color palette selector, I chose “no color”, see below.
The effect is that the points do not appear even though the layer is turned on.
Next, I needed to make the labels orient with the roads. Upon inspection, I discovered that the Roads_Annotation feature class contains an attribute field called TxtAngle. The values range between 0 and 90 and represent the orientation angle of the original CAD annotation.
The default behavior for labels of point features in ArcMap is for the labels to be placed horizontally at a designated location around the point. This works for point data, but not for my line data. Fortunately, the default behavior can be changed. From the labels tab in the layer properties, I chose the option to place the labels at an angle specified by a field in the table. This allows ArcMap to position the labels as they were originally designed in CAD, see below.
Voila! I now have labeled roads, see below. The label font, color, and size can be adjusted to match the CAD annotation, see below.
Now when my client checks data out for use in ArcPad, the Roads and Roads_Annotation layers both can be checked out as reference data. This is an easy way to provide a light-weight and detailed labeled roads layer in ArcPad.
Today we are featuring a guest post from Michele Mattix of Geomattix, LLC. Michele is an expert in the field of GPS and is the author of our GPS e-learning courses including GPS Mapping with ArcPad, Integrating GPS Data with GIS, Introduction to GPS Technology, Adding Digital Photos to GIS, Working with Coordinate Systems in GIS & GPS, and GPS Mapping with Trimble’s TerraSync and Pathfinder Office.
While there are many ways to add digital photos to your GIS, I find that using GPS is the easiest – provided you have a useful workflow. Finding that workflow, however, can be extremely frustrating due to the myriad of GPS and camera hardware and software options. In this multiple-part blog, I will attempt to shed light on this topic so you can find the equipment and workflow that’s right for you. The information for these articles is taken from my Adding Digital Photos to Your GIS e-course.
Georeferenced Photos as Layers
You’ve decided that you want to add digital photos to your GIS. Great! Now you need to determine how you’d like the photos to behave. Basically, you have two options. One is to have a georeferenced photo that is added as its own layer in ArcMap. Because it is georeferenced, the photo is mapped in projected coordinate space so you can see it on your map in its proper location. This method is useful for showing landscape features, perhaps to show how features and terrain change over time. It is also a good way to create a geoscrapbook to document a journey as I’ve done for one of my Sedona hikes, below.
There are a number of ways to use GPS to georeference digital photos. The workflow you use depends on the hardware and software you want to use. The goal of each is the same – assign geographic coordinates to the EXIF header of your photos – a process called geotagging. Equipment options include the following:
- A GPS unit with an integrated camera
- A GPS unit with a connected camera
- A GPS unit with a stand-alone camera and office software for photo-linking
Digital Photos as GIS Attributes
The second way to store digital photos in your GIS is to include them as attributes of your GIS features. Here, the photo itself is not georeferenced but is instead tied to a GIS point, line, or polygon. For example, I maintain a GIS point dataset for Sedona hiking trails called ‘Trailheads’. I store a photo of each trailhead as an attribute of the feature in a field named ‘Photo’, see below. Though the photo will not appear as its own layer in ArcMap, I can use the Identify and Hyperlink tools to open the photo when clicking on the feature.
For this type of GIS photo storage, you will need to create a text field in your GIS attribute table to store the path and name of the photo. You can add your photo paths and names manually in an edit session – just type the pathname in the appropriate attribute table cell. Depending on where you store the photos relative to where you store the ArcMap MXD, you can omit the full path name as I did in the example above. If you only have a few photos, then manually entering the text is acceptable. If you have a lot of photos, however, this method is inefficient.
This is where GPS can help. GPS can automate the photo-linking so that digital photos taken in the field are automatically linked to the appropriate GIS feature. Again, there are a number of workflows you can employ to accomplish this task – each based on your GPS and camera hardware and software tools. These include the following:
- GPS unit with an integrated digital camera and appropriate field software
- GPS unit with a connected digital camera and photo-linking field software
- GPS unit with a stand-alone digital camera and photo-linking software for use in the office
Once you’ve decided whether you want your GIS photos to be georeferenced layers or stored as attributes of other features, you can begin to identify the appropriate GPS, camera, and software tools you will need. In the next article, I will go into more detail about using GPS to geotag your photos.
Michele Mattix is an ESRI authorized ArcGIS trainer and certifed Trimble GPS instructor.Read Full Post | Make a Comment ( None so far )