# Google maps: Where does the lot line data come from? **URL:** \ **Category:** Factual Questions\ **Created:** [March 12, 2010, 1:45pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232 "2010-03-12T13:45:32Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Alienhand](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Alienhand](https://boards.straightdope.com/u/Alienhand)\ **Post date:** [March 12, 2010, 1:45pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/1 "2010-03-12T13:45:32Z")
I’ve seen the lot lines added mainly in cities ([example 1](http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=33618&sll=37.721068,-122.441275&sspn=0.013375,0.01929&ie=UTF8&hq=&hnear=Tampa,+Hillsborough,+Florida+33618&ll=28.060961,-82.495501&spn=0.014921,0.01929&z=16), [example 2](http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=94112&sll=37.715773,-122.459091&sspn=0.006688,0.009645&g=150+minerva+st,+san+francisco,+ca&ie=UTF8&hq=&hnear=San+Francisco,+California+94112&ll=37.718892,-122.436157&spn=0.003026,0.004823&z=18)). The [Wikipedia page](http://en.wikipedia.org/wiki/Google_Maps#Development_history) claims without a cite that lot lines were added in October last year. My assumption is Google simply asked the cities but I actually have no idea. So, where does the lot line data come from? ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [March 12, 2010, 2:01pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/2 "2010-03-12T14:01:40Z")
Most likely it is determined by an algorithm to make a nice looking display. It is most certainly not an “accurate’ surveyor’s plot plan.” Roads and streets on the other hand are determined from the satellite images of the area under consideration. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [March 12, 2010, 2:22pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/3 "2010-03-12T14:22:46Z")
My county auditor maintains a [GIS](http://en.wikipedia.org/wiki/Geographic_information_system) system (yes I know, system is redundant) and all the data is freely available on the internet. I wouldn’t be surprised if plot lines either went to the map data company that supplies Google, or Google integrated the data themselves. ---
**Author:** ![Dinsdale](https://avatars.discourse-cdn.com/v4/letter/d/97f17d/32.png) [@Dinsdale](https://boards.straightdope.com/u/Dinsdale)\ **Post date:** [March 12, 2010, 2:30pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/4 "2010-03-12T14:30:20Z")
While it certainly is not entirely accurate, I have seen numerous examples involving varying and irregularly shaped lots where it resembled reality much more closely than I would think blind logarhithm would. ---
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [March 12, 2010, 2:47pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/5 "2010-03-12T14:47:03Z")
They’re often called shape files, and they are managed by the planning department or the county assessor’s office. Sometimes they’re free, something they’re a few hundred bucks. I assume Google just went out and looked for them. For instance, here are the ones for Tampa, one of your examples: [http://www.theplanningcommission.org/maps/gisdata](http://www.theplanningcommission.org/maps/gisdata) ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [March 12, 2010, 2:48pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/6 "2010-03-12T14:48:56Z")
> [@spingears](#): > > Roads and streets on the other hand are determined from the satellite images of the area under consideration. I’m pretty sure you’re wrong on at least this point. The roads and streets are derived from commercial digital mapping, and often do not coincide exactly with the streets as shown on the aerial images. ---
**Author:** ![Annie-Xmas](https://avatars.discourse-cdn.com/v4/letter/a/ecc23a/32.png) [@Annie-Xmas](https://boards.straightdope.com/u/Annie-Xmas)\ **Post date:** [March 12, 2010, 2:50pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/7 "2010-03-12T14:50:03Z")
Every city is divided into blocks and lots. Part of property taces are based on the size of the lot, the on improvements. The city maintains the tax maps with this information. ---
**Author:** ![Alienhand](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Alienhand](https://boards.straightdope.com/u/Alienhand)\ **Post date:** [March 12, 2010, 3:24pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/8 "2010-03-12T15:24:20Z")
> [@SmackFu](#): > > They’re often called shape files, and they are managed by the planning department or the county assessor’s office. Sometimes they’re free, something they’re a few hundred bucks. I assume Google just went out and looked for them. > > For instance, here are the ones for Tampa, one of your examples: > [http://www.theplanningcommission.org/maps/gisdata](http://www.theplanningcommission.org/maps/gisdata) That is what I was looking for, thank you. Thanks to everyone who responded. ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [March 12, 2010, 3:32pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/9 "2010-03-12T15:32:59Z")
> [@Alienhand](#): > > I’ve seen the lot lines added mainly in cities ([example 1](http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=33618&sll=37.721068,-122.441275&sspn=0.013375,0.01929&ie=UTF8&hq=&hnear=Tampa,+Hillsborough,+Florida+33618&ll=28.060961,-82.495501&spn=0.014921,0.01929&z=16), [example 2](http://maps.google.com/maps?f=q&source=s_q&hl=en&geocode=&q=94112&sll=37.715773,-122.459091&sspn=0.006688,0.009645&g=150+minerva+st,+san+francisco,+ca&ie=UTF8&hq=&hnear=San+Francisco,+California+94112&ll=37.718892,-122.436157&spn=0.003026,0.004823&z=18)). The [Wikipedia page](http://en.wikipedia.org/wiki/Google_Maps#Development_history) claims without a cite that lot lines were added in October last year. > > My assumption is Google simply asked the cities but I actually have no idea. So, where does the lot line data come from? What lot lines? What am I missing? ---
**Author:** ![Angel\_of\_Doubt](https://avatars.discourse-cdn.com/v4/letter/a/7cd45c/32.png) [@Angel\_of\_Doubt](https://boards.straightdope.com/u/Angel_of_Doubt)\ **Post date:** [March 12, 2010, 3:36pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/10 "2010-03-12T15:36:27Z")
Just a note to anyone who wants to use the shapefiles on that site (or any other) - you need a GIS program to use them, like ArcGis or maybe GRASS, which is open source. ---
**Author:** ![Alienhand](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@Alienhand](https://boards.straightdope.com/u/Alienhand)\ **Post date:** [March 12, 2010, 3:46pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/11 "2010-03-12T15:46:08Z")
> [@Leaffan](#): > > What lot lines? What am I missing? The thin gray lines separate from the street outline. If you have the “show satellite imagery” or “show street map with terrain” on you won’t see them, it has to be on “show street map”. You may have to zoom in further to see them particularly for “example 1” in the OP. ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [March 12, 2010, 3:57pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/12 "2010-03-12T15:57:17Z")
I have no idea where they get it but to the best of my knowledge the Australian data is perfectly accurate. We have used it at work for investigations and any address that I know that I look up is accurately represented and correctly addressed. ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [March 12, 2010, 4:02pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/13 "2010-03-12T16:02:54Z")
> [@Alienhand](#): > > The thin gray lines separate from the street outline. If you have the “show satellite imagery” or “show street map with terrain” on you won’t see them, it has to be on “show street map”. You may have to zoom in further to see them particularly for “example 1” in the OP. I wasn’t on “show street map.” Thanks. ---
**Author:** ![suranyi](https://avatars.discourse-cdn.com/v4/letter/s/e36b37/32.png) [@suranyi](https://boards.straightdope.com/u/suranyi)\ **Post date:** [March 12, 2010, 4:43pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/14 "2010-03-12T16:43:58Z")
> [@Colophon](#): > > I’m pretty sure you’re wrong on at least this point. The roads and streets are derived from commercial digital mapping, and often do not coincide exactly with the streets as shown on the aerial images. Not only that but there as some things that aerial images can’t get, that the road and street maps must have. The most obvious are the street names. Next are things like maneuver restrictions, such as “no left turn” signs. This is the industry I work in, so I’m quite familiar with it. As for the OP’s question, if the lot lines are accurate, then Google bought them from a source. I’m not sure what source that woud be, offhand. ---
**Author:** ![enipla](https://avatars.discourse-cdn.com/v4/letter/e/54ee81/32.png) [@enipla](https://boards.straightdope.com/u/enipla)\ **Post date:** [March 12, 2010, 4:57pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/15 "2010-03-12T16:57:49Z")
I’m in the GIS biz too. The data almost certainly came from the city or county. This data is very, very helpfull for the county assessor. More and more of it is free, though we still charge for it. ---
**Author:** ![Angel\_of\_Doubt](https://avatars.discourse-cdn.com/v4/letter/a/7cd45c/32.png) [@Angel\_of\_Doubt](https://boards.straightdope.com/u/Angel_of_Doubt)\ **Post date:** [March 12, 2010, 5:19pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/16 "2010-03-12T17:19:40Z")
> [@enipla](#): > > I’m in the GIS biz too. The data almost certainly came from the city or county. This data is very, very helpfull for the county assessor. More and more of it is free, though we still charge for it. I hope the costs will become more reasonable; my state charges ~$2,000 for parcel data per county and also charges for streets, etc. I want to start a GIS-based business as I can’t find a job in planning or GIS right now. ---
**Author:** ![This\_Just\_In\_2](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@This\_Just\_In\_2](https://boards.straightdope.com/u/This_Just_In_2)\ **Post date:** [March 12, 2010, 5:31pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/17 "2010-03-12T17:31:38Z")
I know of at least one major agency in the Portland Metro area that shares data with Google. In exchange, Google gives that agency 50 licenses for Google Earth Pro. ---
**Author:** ![JoelUpchurch](https://avatars.discourse-cdn.com/v4/letter/j/f05b48/32.png) [@JoelUpchurch](https://boards.straightdope.com/u/JoelUpchurch)\ **Post date:** [March 12, 2010, 5:45pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/18 "2010-03-12T17:45:23Z")
I went to the orange county, florida property appraiser’s web site and found that when I type in a address that it actually has a Google Street button to look at the property. [http://paarcgis.ocpafl.org/Webmap3/default.aspx](http://paarcgis.ocpafl.org/Webmap3/default.aspx) ---
**Author:** ![Lubber](https://avatars.discourse-cdn.com/v4/letter/l/8baadc/32.png) [@Lubber](https://boards.straightdope.com/u/Lubber)\ **Post date:** [March 12, 2010, 7:39pm UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/19 "2010-03-12T19:39:31Z")
At least in Norway basic geodata like these covering most of the country is stored together by Norway digital, I think the dataset is called FKB. Quite handy to get what you need from one place in stead of contacting each municipality/county separately. ---
**Author:** ![Alpine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alpine/32/17813_2.png) [@Alpine](https://boards.straightdope.com/u/Alpine)\ **Post date:** [March 14, 2010, 1:46am UTC](https://boards.straightdope.com/t/google-maps-where-does-the-lot-line-data-come-from/532232/20 "2010-03-14T01:46:14Z")
Another county GISer. You can download our parcel data in GIS format for free from our website. My feeling is that our citizens and visitors benefit by having more accurate data available from Google and other services. I have also been contacted in the past by companies like TeleAtlas and Navteq that create and aggregate geographic data for mapping sites. A company like Yahoo or Mapquest buys the dataset from them. Now if only they would actually _use_ the updated roads data I’ve sent and stop directing people over 4WD passes in the winter…