UPDATE: 20100801 The looping bug outlined below has been fixed.
First, it should be said that adding “Earth View” to Google Maps is a stroke of genius.
- No need to install the Google Earth application
- Links and live embeds to Earth view maps work also
While testing Earth View in the context of my Little Colorado Fly-through Tour, I found a problem with the way Google Maps pans and/or zooms to make a selected place-mark visible. But first, here’s an Earth overview of my user map in progress. Earth tip: try moving the pointer while the button is pressed, and use the Control and Shift keys to change the behavior (rotate compass, tilt camera up, etc.)
View Little Colorado (Grand Canyon) Tour in a larger map
In experimenting with “user maps” using the Earth View feature, it is clear that the Maps place-marks lack the control that the “micro-format” .kml provides — specifically, the view parameters specified in the “lookat” object.
<LookAt id="ID">
...
<!-- specific to LookAt -->
<longitude>0</longitude> <!-- kml:angle180 -->
<latitude>0</latitude> <!-- kml:angle90 -->
<altitude>0</altitude> <!-- double -->
<heading>0</heading> <!-- kml:angle360 -->
<tilt>0</tilt> <!-- kml:anglepos90 -->
<range></range> <!-- double -->
<altitudeMode>clampToGround</altitudeMode>
<!--kml:altitudeModeEnum:clampToGround, relativeToGround, absolute -->
<!-- or, gx:altitudeMode can be substituted: clampToSeaFloor, relativeToSeaFloor -->
</LookAt>
While the view details above can be captured with “link” and “embed,” they are not easily captured in a Map place-mark, except by placing a full Google Maps “permalink” URL inside the placemark.
The default orientation for viewing placemarks in Earth View is due north, where the compass at top left has N at the top (a.k.a. “heading” or “yaw”) at the current zoom level (altitude), and the default camera angle is approximately 45 degrees “up” from straight down (“tilt”)
Casual URL decoding of Google Maps permalinks reveals
“&ecpose=36.18409487,-111.79393673,1482.19,-2.755,44.995,0”
which as expected seem to represent (most of) the six degrees of freedom:
- latitude (X)
- longitude (Y)
- altitude (Z)
- yaw (Z rotation) “heading” i.e. rotation of compass
- pitch (X rotation) “tilt” or camera angle measured from “straight down”
- roll (Y rotation) usually zero, i.e. the horizon is at an angle
- the last parameter may or may not represent “range”
Problems with the Little Colorado river include the narrow canyon, steep walls, and the narrow body of water. Default behavior in Google Maps includes “automatic” view adjustment based on the user’s selection. In the case of the placemark below, many usage patterns leave the placemark invisible, and the algorithm for adjustment often loops and loops and eventually fails, with the view left as shown below.
The addition of Earth View means any place-mark may be invisible in a given view, and the automatic “pan/scroll/zoom” algorithm isn’t quite smart enough yet to handle a few odd cases.
- terrain (elevation) data — a mountain comes between the view and the place-mark
- zoom level of the view — at low altitudes (high zoom), elevation data starts to obscure things
- “heading” (compass rotation) — The view may see the place-mark only if oriented properly
Observing the long looping period it seems what is attempted by the algorithm includes coming closer to the placemark and changing the “pitch” or camera angle. Unfortunately, the “due North” default and maintaining the “zoom” (or altitude) are both problematic.
View Little Colorado (Grand Canyon) Tour in a larger map
Other minor Earth View oddities include the “zoom level” indicator which is always in the center in Earth View, and the fact that “zoom in/out” via the embedded control behaves differently than scroll up/down (the “mouse” equivalents for zoom.) Using a scroll wheel maintains the camera tilt, even if you run into a wall. The zoom out control un-tilts as the altitude increases, and zoom in does the reverse, remembering the tilt that was in effect.
In the process of making many custom user maps, some quirks and deficiencies in Google map making are apparent. Here is a quick list of some pet peeves.
- There is no way to make a placemark that is specifically a “Street view” or “Earth view” flavor. Capturing the “map mode” and view details via permalink URL inside a placemark does work but has problems: there is no other way to switch modes or change the view, and there is no way to tell if you are looking at the exact thing described by the URL.
- There is no way to specify a “place-mark” that includes view parameters other than latitude and longitude.
- Map making is frequently tedious because the tools are unavailable in Street View and Earth View modes. Context is often lost when switching to “regular” map mode.
- User photo icons are vanishingly small in the Earth view mode.
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