Friday, January 13, 2006

Effect of archived caches on World Geocaching Model

Ultimately I want to develop a formula for the number of active caches for any date as one of the parts of my World Geocaching Model. It will be a statistical estimate tracking the growth of geocaching and will allow one to see when geocaching behavior changes and let us determine the factors affecting it, such as season or day of week. The number of active caches on a day is the number on the prior day plus the new caches approved since the prior day. That's not quite right as some caches are archived making them not active and a few priorly archived caches may be resurrected.

Pocket Queries also occasionally return gpx records of caches that have not yet been approved. I haven't figured out how or when this happens, but when I go to these caches from GSAK I get a message saying that I can't see them until they are approved. My GSAK database has information about them that it must have gotten from an earlier pocket query, unless caches can go from the approved state back to the not yet approved state. I wouldn't have expected this to happen. Perhaps I'll explore the issue in more detail in a future note.

In this note I want to talk about caches that are archived. Pocket Queries never return archived caches. They have to be downloaded manually. I use GSAK to probe potentially archived caches and download the single cache gpx files to get the final logs that explain what happened to the cache.

One's GSAK database entries for archived caches present several problems. First, if a cache is approved and then archived before it comes up in the pocket query scan sequence, no record of it will ever appear in the GSAK database. Normally I only refresh existing cache entries from within GSAK for caches that I suspect may have been archived. A couple of times I have sorted my database in waypoint order and then manually brought up the caches with the apparent missing waypoints. This is a slow and tedious process, so I've only done it for a few of the very early caches. Some of the missing waypoints are for caches that were archived before I could get them in a pocket query and some of them have never been used for a cache in groundspeak's system and I get an error.

To use GSAK to find archived caches I sort it on the last gpx date. This places all of the caches priorly marked as archived intermixed with caches that look like they are active but are in front of caches with last gpx date of the just completed scan. If they had not been archived the pocket queries in the scan would have returned them and updated the last gpx date. I call these stale caches. Then I use the split window view in GSAK to view the detail for each of the stale caches. I download the individual cache gpx file for each into a directory and then load all of the gpx files into GSAK at once. Once this has completed, I reexamine the database for stale caches. If I missed any in the process, I just repeat. Sometimes I filter the database on a state or country that has just been scanned with my pocket queries to form a subset that is easier to look at.

My World Geocaching Model will need to account for archiving stale caches and will want to model the factors that affect the length of life from approval to archiving of caches.

The archived cache identification process is quite time intensive. Sometimes has too much activity to be able to return caches in a timely manner and I wait until later when there aren't so many geocachers placing demands on the system. If there are special circumstances where I can identify a group of newly archived caches and can update their gpx records earlier, that will leave fewer caches for later sessions. Event caches frequently are like this and we had a one time mass archiving on January 1st of all locationless caches.

Once the gpx for an archived cache is loaded then the record should never again change. Should a cache be unarchived for any reason in the future, then eventually the world scan pocket queries will pick it back up. It is possible that such re-activated caches will put the number of caches in a pocket query over the 500 limit. In that case there will be a few caches that are not updated on that scan. They will be discovered as still active and refreshed when I do the stale cache process.

Well so much for tonight, I'll post more later. Until next time, happy caching.



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