By Kenneth Field, Esri Research Cartographer
In Part 1 of this blog entry we showed you how to use the Feature Outline Masks tool to convert annotation feature classes to polygon feature classes in ArcMap which can then be added to your ArcGIS.com web map as an operational overlay. This is a great way of adding labels to your web map (figure 1).
Labeling is an easy way to add descriptive text to features. Labels in ArcGlobe are positioned based on feature geometry, and the text strings are constructed from feature attributes. There are 2 types of labels in ArcGlobe: billboarded text and draped text.
Billboarded text is very effective in a 3D world especially when we need our descriptive text above floating layers or 3D objects such as buildings. We can make sure the billboarded text is offset from the 3D objects so it is visible and always facing the viewer.
For example, point features such as schools or fire stations locations can be easily labeled with billboarded text.
Labels for all geometry types can be displayed as draped texture images on the surface of the globe. This is an effective way of adding text to features especially when looking at large areas such as police districts or subway lines when no floating layers are present.
3D graphics labels
It is also possible to place 3D text in our 3D world not linked to a feature class. These are so-called 3D text graphic labels.
Gert van Maren
3D Product Manager
We’ve recently had a few users contact us asking why they
have upside-down labels appearing in ArcGIS Explorer or ArcGlobe. We figured it might help if we explain the
technical reasons behind this phenomenon, and the ways to avoid it, in this
week’s blog post.
So, why are labels
not rotated to the north? Why don’t the
labels spin themselves to the correct angle?
The first thing to know is that this issue only happens with dynamic Map Services. This
particular publishing method takes a request from the viewing application (ie:
Explorer or Globe) and returns the tile in the native coordinate system (which
is Cube). A side effect of this process
is that the service effectively “burns” the labels into the map in the
destination projection – Cube. (This process
of “burning in the labels” is kind of like climbing on to your house and
painting your name on the roof – it locks the text in at that angle). The problem is that in some places in the
world, the map is burning the labels in at the wrong angle.
But why? ESRI knows
which way is north, right?
We do, but the
dynamic map service uses ArcMap (2D) display
logic to create the requested display, therefore labeling objects for the Cube projection
in a way that makes sense in 2D and not 3D.
Let’s look at a graphic. Here’s what the Cube projection looks
like in ArcMap. It’s like a box that folds in on itself for display one a 3D
globe. Note the locations of the North
and South Poles – in the center of the top and bottom sections of the cube.
The Cube Projection, as displayed in ArcMap
Let’s look closer at the North Pole area. You
can see how there are actually four sections inside the polar faces, and that
the “north” direction is separated into four regions (triangles). Note that the labels are appropriate
(readable) for viewing this in 2D.
The blue arrows indicate the north direction within each triangle
If we think about those triangles rotating into
place (to honor their true north direction) it’s possible to grasp how the
labels are being displayed with 90-degree rotation in Greenland, 180-degree
rotation (upside-down) in Europe, and 270-degree rotation in eastern Russia.
Rotating the polar sections so they display a
consistent north direction.
OK, so now you understand the technical details of what
But most likely you only really
care about how to fix it. There are a
number of options to publish services that AVOID this issue. A few of the
simpler workarounds include:
Fully cache the Map Service (in, say, WGS84 or
Fully cache a Globe Service
Create a fully cached vector Globe Service for the labels (point features only), and publish
the non-labeled layers as a Map Service
Of these options, you may find that the third provides the best
final display. While it does require the
creation and maintenance of an extra service, the display of billboarded labels
in 3D is usually the most effective.
One of the new features introduced with the latest release of ArcGIS Explorer Desktop (build 1500) is the ability to label notes. By default the title associated with a note is displayed as a tip when you hover over the note.
For point notes you can now change the display of the title to be shown as a label. Select the notes you want to label, right click, and choose Labels instead of Map Tips.
All of the notes will be labeled, but to avoid label conflicts the labels that are shown will vary as you zoom in or out. Surrounding labels will change to display the title as a tip for easy identification until the zoom level is such that no other labels intersect it
You can also set this by using the the label options in the Symbols group of the Appearance tab for notes.
Labels and Map Tips can be set for each individual point note, just select the one you want and make the appropriate choice from the appearance tab or by right-clicking to open the note properties.
For more information about working with notes and setting note properties, see the following Help topics: