Guest LoCache Posted August 22, 2001 Share Posted August 22, 2001 I have been on the Geocaching site for a while now, and it has said from day one : "We couldn't find your zip code in the database. This is probably because our zipcode database uses information freely available from the 1990 census. I would suggest subtracting 1 from your zipcode to get a close approximation of your location. We'll try to get more up-to-date data soon! " WHEN?! I can't stand that I can never get accurate info in my area. I have dealt with it though figuring it was mostly an issue with my area which recently changed...then recently I tried a friend from another state's zip and it did the same thing....is this happening to a lot of people out there? Just wondering. Geo Quote Link to comment
Guest Markwell Posted August 22, 2001 Share Posted August 22, 2001 Instead of a zip code search, try the "advanced search" on the Seek a Cache page, and do one based on your Lat/Lon. It's much more accurate. The 60544 zip code I would use for Plainfield, Illinois, is about 3 miles from my house, so I search based on my Lat/Lon. Quote Link to comment
Guest Markwell Posted August 22, 2001 Share Posted August 22, 2001 Instead of a zip code search, try the "advanced search" on the Seek a Cache page, and do one based on your Lat/Lon. It's much more accurate. The 60544 zip code I would use for Plainfield, Illinois, is about 3 miles from my house, so I search based on my Lat/Lon. Quote Link to comment
Guest Snowtrail Posted August 23, 2001 Share Posted August 23, 2001 Yeah, I don't know how the zipcode thingie works either, but one of the downtown caches on my page is listed as being 20 miles away even though I only live 2 miles from downtown. Use the lat and long. It really is more accurate. Quote Link to comment
Guest Qman Posted August 23, 2001 Share Posted August 23, 2001 If you believe the search system to be accurate because it found your zipcode your mistaken. The post office assigns zipcodes to streets (or buildings) for mail delivery purposes.....nothing else. In most residential cases, zipcodes are not points but streets or street sides. To represent a zipcode as a single point (which this system does), you are at best using a mathematical approximation of the center of the zipcode and comparing the lat/lon from the cache location to the center of your zipcode. So, it only has the potential to be "accurate" if you live close to the center point of your of your zipcode. The lat/long with the 1990 census data is the mathematical center of the geographic area regardless of the distribution of housing units within the area. Having said this, I'm not critizing the folks who setup this site because it quite works well within the restrictions of the data being used. The only way for it to be better is to enter your address and have it determine the lat/lon and search by that. But that's Markwell's point, the most accurate search would always be obtained by entering the lat/lon of your house. Quote Link to comment
Guest jeremy Posted August 23, 2001 Share Posted August 23, 2001 Geocoding is an expensive proposition. However, I may be able to get one soon. In the meantime you can use the lat/lon lookups if zipcode lookups don't work for you. You're right about zipcode lookups being a spotty thing, but remember that there are entire industries around geocoding, and it ain't cheap. Jeremy Quote Link to comment
Guest LoCache Posted August 23, 2001 Share Posted August 23, 2001 Thanks Jeremy! It's not a big deal, just wondered if it was even something in the works to be updated...I rarely try to use it myself, but when I do it annoys me. Thanks for the info. Geo Quote Link to comment
Guest jeremy Posted August 23, 2001 Share Posted August 23, 2001 I checked the census site and, unfortunately, they've moved away from using postal zipcodes. As a result I'll have to find a better way to do geocoding. I was hoping that the 2000 census would have a more accurate postal zipcode database, but that doesn't seem to be the case. Jeremy Quote Link to comment
Guest ManuelCasi Posted August 23, 2001 Share Posted August 23, 2001 Jeremy, I think I remember reading in a fourm some where in which I think it was you that stated that the zipcode search results where from the postoffice in that zipcode to the the cache. That is the distance to cache was measured this way. Is that the case or do I have early sighns of old age? Quote Link to comment
Guest jeremy Posted August 23, 2001 Share Posted August 23, 2001 You're correct. It's where the post office *was* as of 1990. So rural areas with only one post office can be a huge area. And I don't take into consideration the ZIP+5 codes. Jeremy Quote Link to comment
Guest Qman Posted August 23, 2001 Share Posted August 23, 2001 Jeremy, Can you tell me more about the Census 2000 zipcode data that you'd like to get for this site? Maybe the data are available but in a different format. I have a bit of an inside track so I might be able to help you. It might be better to email me directly to discuss the details. My email is cbest@census.gov Quote Link to comment
Guest jeremy Posted August 23, 2001 Share Posted August 23, 2001 It's pretty straightforward really. a basic table of zipcodes, lat,lon, city, state. Jeremy Quote Link to comment
Guest Qman Posted August 23, 2001 Share Posted August 23, 2001 City/state? Is that the city/state(s) associated with the actual zipcode area or where the post office for that zipcode is physically located? The post office location would be a 1 to 1 relationship but if it's based on the geographic area of the zipcode, it would be a 1 to many. My zip is 64152 the post office calls Kansas City, MO. However, the zip includes parts of several cities. There is cartographic boundary file available now called the ZipCode Tabulation Area (ZCTA) that's available in shp, e00, or A/i ASCII that includes polygons and zipcodes. Probably wouldn't take much to get ArcView to cough up the lat/lon. Quote Link to comment
Guest martinp13 Posted August 23, 2001 Share Posted August 23, 2001 quote:Originally posted by jeremy:And I don't take into consideration the ZIP+5 codes. Gosh... and here I thought ZIP+4 was advanced! ------------------ > Martin Magellan 330 (1.56/WAAS enabled!) Don't have time to program and record your shows while geocaching? Get a TiVo ! Quote Link to comment
Guest martinp13 Posted August 23, 2001 Share Posted August 23, 2001 quote:Originally posted by jeremy:And I don't take into consideration the ZIP+5 codes. Gosh... and here I thought ZIP+4 was advanced! ------------------ > Martin Magellan 330 (1.56/WAAS enabled!) Don't have time to program and record your shows while geocaching? Get a TiVo ! Quote Link to comment
Guest jeremy Posted August 23, 2001 Share Posted August 23, 2001 oops. Slip of the keys. Quote Link to comment
Guest jeremy Posted August 23, 2001 Share Posted August 23, 2001 oops. Slip of the keys. Quote Link to comment
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