« Offices or Cubicles? The Eternal Debate Continues… | Home | How to Make a Million Bucks in a Few Months »

Dec

5

Of Points and Parcels

By: David Gibbons, Director of Community Relations | December 5, 2006 |

Update 3/31/2008: If you post a Make Me Move (or For Sale price) on your home, you’ll be given the option to edit the home’s location on the map. In the future, we hope to enable anyone who has claimed a home to move their home, but the site doesn’t have that capability yet.

Let’s talk about maps. By the time you see your search results on Zillow, at least five information sources have been dynamically cross-referenced to display the map. Rendering maps is a complex process and, as with Zestimates, the accuracy of mapping on Zillow is dependent on the accuracy of the information we have about your house and neighborhood. In this post I’ll explain how we position houses on Zillow’s maps and how the data we have can impact the accuracy of those maps.

We use one of three methods to locate houses on Zillow’s maps. I’ll explain how to recognize each method but first let me answer the most common question about mapping inaccuracies, namely: “My house is in the wrong place on the Zillow map, does that impact my Zestimate?” The answer is; no, when calculating Zestimates, we only consider the raw public data about the house and don’t “look” at the maps. Therefore, if we incorrectly placed your house on top of your neighbor’s home on the map, don’t worry — your Zestimate will not be thrown off by mapping inaccuracies. The same applies to satellite images that are out of date — if the satellite image does not show your recent remodel but the county tax records do, it will be considered in calculating your Zestimates.

Let’s take a look at each of our three mapping scenarios. Positioning a house on a map requires more than an address. All three scenario’s use geocodes to position properties on maps. Wikipedia defines a geocode as a geographical code to identify a point or area at the surface of the earth.

The most accurate way to describe the location of a property is by describing the boundaries of its land parcel. This is our preferred and most precise scenario. The parcel boundary information is geocoded by your county who keeps accurate records of geocodes for each corner of the property’s land parcel. In this scenario, we render the exact parcel boundary in our search results. You’ll know that we have parcel information in your neighborhood if your lot is outlined like those in this Seattle neighborhood (below).

Parcel

If we don’t have parcel information, we use a single point to locate houses in search results. You can tell that you are looking at search results that use points and not parcels if houses are represented by small blue diamonds on the map. The other two scenario’s both use points — which are essentially a single geocode for each home. In the more precise of the two point-based solutions, we have geocode information for the (rough) center of each property. So, while not as exact as a parcel outline, this method fairly accurately locates a house where you’d expect to see it on the satellite image (as seen below).

Point_1

The last and least precise method of mapping is shown in the final screen-shot (below). Here, we have had to derive a point location with no more information than the house’s address and the location of the street it is on. Wherever this method is employed, you will see “approximate map location” in the bubble that appears in your search results.

Point_2

Our parcels database has grown significantly since we’ve launched and we continue to focus on collecting more parcel detail across the country.

Last 5 posts in FAQ

Share and Enjoy: These icons link to social bookmarking sites where readers can share and discover new web pages.
  • Digg
  • del.icio.us
  • Reddit
  • SphereIt
Topics: FAQ, Zillow |

Enjoy this post? Subscribe to the Zillow Blog feed or get updates via e-mail

Enter your email address:

Delivered by FeedBurner


Comments

25 Comments so far

  1. Chrishar on December 7, 2006 6:08 am

    My home has a blue diamond, but there’s much more wrong than just the location. I contacted you about my house being shown several parcels down the street and despite it being less than 1 year-old construction. Recently purchased properties should be worth roughly the same as the price paid, but in my case, the zestimate is listed at about 20% LOWER. Similar, new homes in my area are selling for about 20% MORE than what I paid less than a year ago. (That’s selling, not listing for more)

    I’m convinced that my address was mapped to a lower priced property down the street, as shown on the map. Additional evidence for this is the fact that the number of bedrooms, property type and number of stories are wrong. Could all of these really be incorrectly listed for a home that was built a year ago???

    I love the service, but I just want to throw this out there: you guys are failing if you have to explain this stuff in such detail. Make it easier.

  2. mdwebneck on December 16, 2006 1:13 pm

    DITTO sortof
    All the addresses on my street are mapped incorrectly and I don’t mean next door or out in the street, I mean two blocks away in an easement or on another street altogether.
    Being a lot off is what I would expect of google etc, but a site like http://www.mdmerlin.net/atlaslaunch.html

  3. Charles Farrugia on July 15, 2007 1:42 pm

    My home in the Portola district was marked as an Excelsior home on Zillow.com. Not only is this in error but it will be sure to bring property values down, being the Portola is been much less prone to crime and much more family friendly because of its many parks and schools. Portola Park and playground still exist as does Portola library on San Bruno St. What gives?

  4. Robert Abelson on August 15, 2007 7:07 pm

    Why do you only show all parcels in the field of single family residentials or condos.

    Since you have all of the Assesors information and parcel maps why not display the Assessors Parcel and the property information. I realize that the Zestimator will not work for these types of properties.

    Otherwise can you direct me to a website or service that show assessor parcels and both aerial and birds eye photos for Southern CA.

  5. David G from Zillow.com on August 16, 2007 5:06 pm

    Robert -

    To avoid confusion. Zillow currently specializes in single family homes. If we displayed all parcels our site’s users would want to know why so many are missing Zestimates. We may eventually expand the site to other types of property but before we do it’ll need significant redesign of features and content.

  6. Lee McLeod on August 18, 2007 3:22 pm

    I can’t get the map to come up on my screen. It was there one minute and gone the next. It won’t come back. What can I do?

  7. David G from Zillow.com on August 20, 2007 2:09 pm

    Lee -

    This page describes solutions to the more common search problems when using Zillow:
    http://www.zillow.com/wikipages/Troubleshooting-Search-Errors-on-Zillow

  8. ce2 on August 30, 2007 10:53 am

    Can someone please tell me if the aerial photos can be downloaded as a georeferenced image and saved into a jpg or tif file? Thanks.

  9. Amanda jones on October 18, 2007 4:42 pm

    I have claimed my poperty but it will not show my house #, just the street name and a little house where I am on the block. The “house” location is correct but it will not update my street #. I live at 405 Boone Valley Dr, 78664. My next door neighbor is 409 and his is correct. Also, it only shows plots of land, no house. When does that update? Our block has been completed for over a year. How often do you get new images.

    Thanks
    Amand

  10. Drew Meyers on October 18, 2007 4:57 pm

    Amanda-
    Thanks for the heads up - we’re looking into this issue of the missing house #’s. I’ll post an update once we have some sort of answer for you.

    Regarding the aerial photos, they come from a variety of aerial and satellite providers and each are continually trying to keep their imagery current. However, our maps may be several years old in some places (such as yours in this case).

  11. Bridget Smith on November 7, 2007 12:02 pm

    As with many others, all the house numbers for my street on your map are incorrect. It looks like the detailed information is correct in association with the house number, but the locations are all off. My house is 104 Hillcrest Circle, 89403 and is listed as 129. The house across the street from me is 101 and is listed as 129. If there is any way to correct this, it would be appreciated. Also, the aerial photo is pretty old since it shows that the neighborhood is not fully built out and it has been for several years. I’m not sure how often these photos get updated, but just to let you know that this is definitely old information. Thanks.

  12. PHIL BERG on November 26, 2007 1:42 pm

    THERE IS NOTHING CORRECT ABOUT MY HOUSE….

    SQUARE FOOTAGE IS OFF
    LOT SIZE IS OFF
    LOCATION IS OFF
    PRICE IS WAY OFF

    NOTHING IS CLOSE…..

  13. KC on November 26, 2007 3:23 pm

    I PUT IN THE WRONG ZIP CODE. THUS THE MAP IS OFF. IS THERE ANYWAY TO EDIT THIS?

  14. David H on January 5, 2008 12:30 pm

    Can you please update the map around Anson Drive, Silverwood Trail in zip code 29229? These streets have been here for almost two years. If you google the map, all of the streets are there — on zillow, they are not yet mapped. Your help is greatly appreciated!

    Thanks,
    David

  15. Linda C on January 13, 2008 7:44 pm

    Hi, I keep waiting for Zillow to show the homes in my neighborhood, they are 2-3 years old and they aren’t showing up on your maps. 31 homes have been built in this development and there is data going back 3 years on all of them for price. Some have sold twice. The map doesn’t show any of the new roads that have been paved and named for 3 years. Can you please check with Google Maps link I provided below, you can see all the new development within a half mile of my home in all directions. Just wanted to give you some help, love your website! Here are the coordinates and link for fairly recent map:

    1643 Ivey Church Rd, Maiden, NC 28650
    Link:

  16. Linda C on January 13, 2008 7:45 pm

    1643 Ivey Church Rd, Maiden, NC 28650
    Link:

    Here is the link, it didn’t show up above for some reason.

  17. laith hadi on February 11, 2008 8:00 pm

    Hello
    my two properties on the map are at the wrong location so can you please fix it thank you. my addresses are
    1100 North mooney Blvd, visalia, ca
    1110 North mooney Blvd, visalia, ca

    Thank you,
    Laith

  18. Laura on February 25, 2008 11:29 am

    When I enter my address and look at the aerial photo, it is a photo of the house next door. Of course when I enter the house number for the one on the other side of me, the photo is of my house. This then creates misinformation regarding size and value of each home.

  19. Gail on March 8, 2008 5:25 am

    You are showing my neighbors house, please get the right property and adjust my value. Thanks

  20. regis pautrat on March 9, 2008 12:07 pm

    you have my neighbor’s house at my address

  21. regis pautrat on March 9, 2008 12:09 pm

    you have my neighbor at my address thanks for fixing it soon

  22. Corey Robb on March 27, 2008 12:57 pm

    Your map is all wrong. My home is on the conner of Swan Dr and Riverview dr. Your map shows it halfway down the street. You have to update your information and get it right. This is very disappointing. You had it right last year when I first checked on my home so whats up. We certinly hav not picked up the house and moved it. Please get it right. Shame Shame on you.

  23. Art Haffey on May 7, 2008 6:24 pm

    Recently while entering a couple of new listings, when it showed the aerial photos, and gave me the opportunity to reset where my listing was on the photo, there was not a little house, that showed where my listing was.
    Do I need to download a program, so that I can see where my listing is located on the map?

  24. joyce on May 9, 2008 1:43 pm

    How do you cancel or delete a Make me move? or anything else on Zillow for that matter????

  25. Drew Meyers on May 9, 2008 2:14 pm

    Joyce-
    Log-in to your zillow account, navigate to your home details page, and then click the “remove Make Me Move” in the tool section on the left.

Name (required)

Email (required)

Website

Speak your mind