Win7+Internet Explorer: GeoJSON example invalid object

[markpet49]

Description

When running the GeoJSON example, the example stops loading with the following error:

GeoJSON.parse: invalidGeoJSONObject.

Operating System and Version

Windows 7/IE 11

[AkeluX]

The problem seems to be a character in the input file that the JSON parser in IE 11 doesn't understand:

SyntaxError: Invalid character\n at GeoJSONParser.prototype.parse (http://192.168.99.1:8080/build/dist/worldwind.js:50524:17)\n at Anonymous function (http://192.168.99.1:8080/build/dist/worldwind.js:50501:25)

[AkeluX]

The invalid character is in https://worldwind.arc.nasa.gov/web/examples/data/geojson-data/world_main_cities.geojson. I haven't identified which one.

@pdavidc @markpet49, as this is not a bug in the GeoJSON parser itself, I propose to postpone this issue.

[markpet49]

@AkeluX FYI, I researched this a bit and it appears to be related to a size limitation for JSON strings in IE. If you shorten up world_main_cities.geojson, for instance, the problem goes away for that file. Initially, I thought it was related to unix style line endings, but that turned out not to be the case. The reported error message is misleading.

[pdavidc]

Here's a summary of what we've decided:
• Replace the file world_main_cities.geojson with one small enough to fit within the IE11 JSON size limitation.
• Document the IE11 JSON size limitation in the GeoJSON API docs.

[AkeluX]

@markpet49 The current world_main_cities.geojson works on IE11 when I serve it from my local computer. I've also discovered that world_borders.geojson is actually 2MB larger than world_main_cities.geojson and works fine from worldwind.arc.nasa.gov. I guess the problem goes away when shortening the file because we remove the problem from the file, but it does not seem related to its size.

@pdavidc I propose to go ahead with the release plan and continue investigating the cause for this issue independently. What do you think?

[pdavidc]

@AkeluX This sounds good to me.

[markpet49]

@AkeluX Hi Yann. I dug in to this some more. You are correct that it is not size related. There are a number of non-printable (>0x7E) characters in the file. To see their location, I executed the following commands (on unix):

cat -v wmc.geojson >wmc-cat.geojson
diff wmc.geojson wmc-cat.geojson

A quick fix is to clean the file with the following command:

tr -cd "\11\12\15\40-\176" <wmc.geojson >wmc-clean.geojson

After this, the file loaded fine, but some of the place names with non-printable (>0x7E) characters may have spelling issues. However, they are not likely to be spelled correctly with the current version.

[AkeluX]

Thank you for looking deeper into this. Just as a thought, could it be that this file is encoded differently, e.g. UTF-8 vs UTF-16?

[markpet49]

@AkeluX Good thought, but many of the occurrences look suspiciously like garbage characters. Examples (with an exclamation point at the non-printable character position): "Amundsen!Scott South Pole Station" and "San Mart!n Station". I estimate about 100 lines out of 1200 have the issue.

[AkeluX]

The new files proposed in #450, which are in UTF-8, also fix this issue! This screenshot was taken in Win7/IE11, see Lulea and Malmo.

[AkeluX]

Fixed via the action taken in #450.