Of Points and Parcels
By: David Gibbons, Zillow Director, Community Relations | December 5, 2006
Update 9/30/2008: Any owner or listing agent is given the option to edit the home’s location on the map by navigating to the home details page and clicking the “edit location” link in the tools section on the left side of the page.
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 The same applies to satellite images that are out of date — if the satellite image does not show your recent remodel but the county tax records do, it will be considered in calculating your Zestimates.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).
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).
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.
Our parcels database has grown significantly since we’ve launched and we continue to focus on collecting more parcel detail across the country.
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Comments
46 Comments so far
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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.
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
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?
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.
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.
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?
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
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.
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
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).
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.
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…..
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?
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
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:
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.
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
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.
Gail on March 8, 2008 5:25 am
You are showing my neighbors house, please get the right property and adjust my value. Thanks
regis pautrat on March 9, 2008 12:07 pm
you have my neighbor’s house at my address
regis pautrat on March 9, 2008 12:09 pm
you have my neighbor at my address thanks for fixing it soon
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.
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?
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????
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.
beth houts on May 15, 2008 5:35 am
you have us listed in the wrong place. our home is not a barn how do we fix the location
Nina on June 17, 2008 4:41 pm
I am unable to select my house on the map. When I place the house icon where it is supposed to be and save, it defaults back to the wrong position…help!
Thanks!
Nina
Jimmy Cox on June 19, 2008 11:42 am
The map for my home is correct, however, the birdseye view photo of my home is of my next door neighbors home. What’s up with that?
David Gibbons on June 19, 2008 11:54 am
Jimmy -
I’m guessing you live on a hill. Positioning of oblique aerial imagery on a map is done by triangulating the location of the home with the assumption that the airoplane’s altitude above the subject property is constant. When you start taking photo’s of homes on a hill it throws that off. Microsoft have implemented algorithms to correct this that uses some understanding of local topology but it’s not 100% perfect.
Corinna Lee on July 23, 2008 10:10 am
Our house address is 12858 Skyline Drive, Plainfield, IL . It is located at the corner of Pastorial Drive and Skyline Drive.( A corner lot.)Your map shows our house as the fifth house from the corner.The birdeye view of our house is also the house of our neighors, which is the fifth house from the corner.
George Gust on July 29, 2008 2:17 pm
My house address is 16317 NE 30th Ave., Ridgefield WA. The aerial photo is accurate, but the street level photo is of a house one block over at 16317 NE 29th AVE. In fact, all the street level photos of homes on NE 30th, show houses on NE 29th. Can this be fixed?
Jim Crain on August 1, 2008 1:50 pm
I looked at your site for the first time today. The Satellite shows our home, in fact we were the first on the block, but there was no value on our home. The diamond is in our neighbor’s front yard. When I posted information on my home that is larger than several homes around me, my value is lower. All of the school information for our neighborhood is the wrong school district. If you are going to put this site out for others to compare there is far too much incorrect information for it to be usuable.
Tony Caine on August 15, 2008 11:04 am
The north property line of 960 Neilson St 94706 on your map is curved. The property line on the official parcel map of the alameda county assessor is straight. What data did you use to construct the line. If it is from the Alameda County assessor, how do I contact the assessor and describe your data source to determine this reason for this contradiction?
Tony
Elizabeth on August 27, 2008 12:33 pm
The cottages at 2750 Kalapu are located at the corner of Puukolii and Kalapu not at the corner of Kalapu and Kolepa.
When Zillow makes a Zestimate it uses the Kalapu cottages as comps for Single family dwellings on Kolepa. The homes on Kolepa are single family dwelings. The cottages on Kalapu are condo homes. The cottages and the single family dwellings are separated by the golf course and are 2 different neighborhoods.
This mistaken location has brought Zestimate values down on the single family homes on Kolepa.
Would changing the correct location to the corner of Puukolii and Kalapu be difficult?
Lorraine Moore on September 23, 2008 11:58 am
I can understand everyone’s frustration with incorrect info on Zillow. My house facts and location are all wrong: I have two single family homes on one lot. The main house which was completely renovated from a condemned state in 2007 is 5 bedrooms, 3 baths but shows as 3 beds, one bath which is actually my neighbors home. The photo for mine shows at my neighbors address. That aside, I’m a Realtor. I have to deal with this mis-information on a daily basis. If I had a dime for everytime a client said “but on Zillow its this much” I’d quit working and retire. Zillow could be a pretty cool tool if it could be even slightly accurate. I tell folks to totally disregard Zestimates because it truly hurts when you are trying to market your home.
K. Hall on October 11, 2008 10:12 am
You used to have the correct photo for the front of my home, but today I noticed you do not. the photo you are now showing is for another house on a nearby street that has a similar name but not the right street. How can you fix it?
Emily Werrett on October 25, 2008 8:50 pm
My house is 5601 Savannah Woods Lane, Rosharon, TX 77583, and when I edited the location of the house on the map when I first posted my listing, it updated and didn’t put the blue diamond in the right spot. It is miles and miles away. How do I edit this?
Chris Wash on November 12, 2008 10:57 am
The Zillow map editing program doesn’t work correctly. I tried to relocate my house to its correct place, but the program would not save the edited locations correctly - it kept moving the house icon somewhere other than where I put it. It’s very frustrating and needs repair.
doris silva on November 17, 2008 2:51 pm
i punched in my address to get some compatible info on houses in my area and my address came up with a completely different house!
doris silva on November 17, 2008 2:54 pm
my address came up with a totally different house on it. how can this be fixed?
G P on December 2, 2008 1:11 pm
I am trying to fix the location of my house which is shown a few parcels away from where it should be (and that makes a huge difference for someone looking to buy it) and no matter how many times I move the little diamond that is supposed to show my house location, when I save it, it always lands in a random and totally wrong location. How to fix this? Please advice.
T D on February 4, 2009 4:06 am
While updating the details of my home, I am trying to position the diamond at least near my actual address for prospective buyers to have a chance at finding it. I can position the diamond, but it will not save at the location in which I positioned next to my house on the aerial map. Any ideas?
S. Cook on June 1, 2009 10:20 am
You show 1.1 acres alright, however, you show HALF of our property and HALF of our neighbors. You don’t show my house but you show half of our neighbors house. What gives? My lender is going to require a $2,500 survey because of Zillow. Shall I send you the bill? I see all the explanations for incorrect sites, so you should advise lenders NOT to use Zillow as a reference.
j w on July 16, 2009 4:39 pm
Your aerial map shows the middle school at the wrong address - the place it points to is a SFR (warren e. hyde - cupertino,ca). Because its in the wrong location, all the houses in my area show the wrong middle school. Its actually on corner of miller and bollinger. Please fix.
Wendy on January 9, 2010 1:19 pm
I am desperately trying to correct an incorrect aerial photo that is displaying on the zillow.com site. The aerial in the photo is of MY property, which is not for sale nor is it in foreclosure. The property listing, for my next door neighbor’s house, was placed by foreclosures.com. I have tried to work with them to get this corrected. Zillow has not been cooperative at all and has referred me to the listing source.
At this time, it’s still showing my home.
This is horrible. I feel like my privacy and my reputation are being invaded, without my permission.
I need to get this corrected at once.
Debbie Sheetz on January 17, 2010 7:14 pm
the schools for my town Harvard, MA are incorrect. It says there is no high school and no middle school. We have one of each. Then it refers to a middle and high school in another town as the “nearby” schools to our house, but that is not correct. It also lists a private nursery school as an elementary school, and that is also incorrect.
It does list our actual public high school and middle school under “Other Schools” — I have no idea why.
Our public schools are a major contributor to property values in our town, so it makes me wonder what the estimates are based on.