HELP: Accuracy of web-based Address Geocoders

 

I search POI Factory regarding this issue and could not locate any relevant posts.

I maintain a POI file using several address geocoders. I recently noticed that my Garmin would occasionally lead me to a location across the street from the actual address desired. I was very surprised!

My primary geocoder is MyGeoPosition.com. I find that alternate sites like geocoder.us or GPS Visualizer could not always identify inputted addresses. These addresses are on well traveled main streets in urban locations.

What am I missing here?
What else can I do to improve the accuracy of my POI's?

TIA.

--
“It’s their world. We’re just living in it.”

Those address geocodes, and

Those address geocodes, and the Garmin unit itself are limited in accuracy by the data base it draws from. Wrong side of the street usually means the addresses supplied by the locality GIS is not exact.

--
Frank Nuvi 3597LMT 37.322760, -79.511267

What I do

is use EPE to move the marker. It uses google for its map.
Pull your original file in to EPE and look at the locations that are wrong. If you identify them, move the marker, resave the file and upload back to the site since I assume you are a maintainer for the file.
You can also look at other maps to just verify accuracy.

--
Nuvi 2460LMT.

Another Way

While I agree with pwohlrab that EPE is the best tool to use to fine tune your geocoding, EPE has a pretty steep learning curve.

If you are familiar with BaseCamp, another approach would be to open your POI file and under the “view” tab, select “view in Google Earth”. You must first have Google Earth installed on your computer. The location of your POI file coordinates are now displayed by push pins.

Often, you can spot the real location of your POI on the Google Earth image. You can switch to Google Maps and street level view from within Google Earth to enhance your search. Sometimes, you can spot your POI in user uploaded photos by clicking the screen icon.

Once you find the actual location of your POI visually, you can then correct the POI coordinates using BaseCamp. I often boot BaseCamp and Google Earth side by side as a split screen to make the process easier.

Keep in mind, there are position errors involved with consumer grade GPS equipment and even in Google Earth itself. The magnitude of these errors varies with location so don’t try to put too fine a point on your POI positioning.

Geocoding

Geocoding is becoming better but still is far from perfect. I also use EPE and often side by side with Google Earth Street View to nail down where something really is.

--
"There's no substitute for local knowledge" nüvi 750, nüvi 3597

@e_piph_a_ny

e_piph_a_ny wrote:

...
What else can I do to improve the accuracy of my POI's?

While EPE does take a while to "master", it is very straightforward as far as locating POIs. When I was asked to take over the Jo-Ann Fabric and Craft Stores POI File, I found EPE invaluable because of the fact that the "Edit" dialog contains a "Google" panel.

Let me start by assuming that you have a file of addresses and then we will walk through EPE.

Start by going to
Downloading and Installing EPE
and follow these instructions to get EPE on your computer.

Then go to
Configuring EPE
and follow these instructions.

Next, while in EPE, click on Options > M-column CSV fields

Make these changes:
Col 1 = POI Name
Col 2 = Address
col 3 = Post Code
Col 4 = Latitude
Col 5 = Longitude
Col 6 = state
Col 7 = (not used)
Col 8 etc all (not used)

Then in the Change Selected Profile Name: field, type Geocoding
(and the name is your choice)
Finally, ckick Close.

Now, cut and paste the following into Notepad

Quote:

name,address,city,zip,lat,lon,State
tullahoma,1600 jackson st,tullahoma,37388,,,tn
knoxville,154 N Peters Rd,knoxville,37923,,,Tn
somewhere,1923 Old Fort Pkwy,Murfreesboro,37129,,,TN
someplace,1189 Vann Drive,jackson,38305,,,tn

Click File > Save As> and type "Geocoding.csv" into the File name field (and you need to include the quotes). Finally, click Save

Now, go back to the open EPE and click File > Open and navigate to the "Geocoding.csv" file that you just saved.

EPE will complain that there is an "Invalid CSV Line" because your file has no valid longitude and/or latitude in line 2. Of course, we know that because our goal is to geocode addresses. So - first check the box next to "Apply to entire file" and then click "ignore".

EPE will load 4 POI lines. Now let's take note that our "header" line in the file "Geocoding.csv" was not in the "standard" Garmin order for comma separated files. Indeed, the names of some of the fields in this header were not the same as what EPE would have used (eg. zip vs Post Code). Also, note our POI Names were random choices on my part since all of these entries are actually Jo-Ann Fabric and Craft store entries in the POI-factory file I maintain. In other words you can be pretty loose with names.

All I wanted to illustrate is that exactness is not something you have to agonize over.

Ok, now let's try geocoding. Click on Tools > Batch Geocoding. EPE will attempt to geocode and in this example will come back with "Some POI entries could not be geocoded. Do you want to open the log in Notepad?" Click Yes, and the log will show

Quote:

Geocoding Log - The following POIs were not geocoded:

POI 1: The requested search did not return any relevant result

What this says that "POI 1" failed to return relevant results - ie. it failed to geocode. (As you might imagine, I knew this would happen since I had the same problem when I was creating the Jo-Ann POI file)

So let's see what the POI 1 looks like. Left double click on it. and you will see

Quote:

Name tullahoma
Address 1600 jackson st
City tullahoma
State tn
Post Code 37388

Well, it turns out that that is exactly what the www.joann.com website shows as the address. You can go to http://www.joann.com/stores
and type in tullahoma, tn in the search field and click search. Why the response comes back like it does is beyond me, but it says there is 1 store that was found "in your area" but then shows me a store in Wichita, KS first. Anyway, the store we want has this address

Quote:

1600 Jackson St. Northgate Mall
Tullahoma, TN 37388

Back in EPE, you can - as I did - try various iterations of the address, including putting the number to other values, but nothing worked for me at that time (more on this later).

So, what I did was to close the "POI Edit - tullahoma dialog. I then did a Tools > Open in Google Earth. I don't know where you will go, but it put me in the middle of the ocean. Not to worry, I typed "joann fabric near tullahoma tn" in the Search box and clicked Search. Earth took me to a Jo-ann store with the same address as the www.joann.com website.

If I moved my cursor to the bottom tip of the red teardrop icon, at the bottom of the Earth page were the coordinates "lat 35.379350 lon -86.225799" which I could use to locate the Tullahoma store.

So leave Earth open and go back to EPE. Double click to open the POI Edit dialog for the tullahoma store and enter the coordinates (and remember EPE expects lon, then lat). Once these are entered and you "Tab" out of the latitude field, you will see the Google map in the upper right pane of the POI Edit dialog.

Click the plus arrow a couple of time to zoom in and get the label "Jo-Ann Fabric and Craft" to appear.

Now for some of the other near things you can do. Click on Satellite in the upper right corner of the map; then, grab the "yellow man" icon in the upper left and drag it to the intersection from which you would approach the store and drop it there. You will now be in Street view. In this case, grab the "N" box in the "Circle" and drag it around to the left (which causes the street view to rotate around to the right until you see the "Jo-Ann" on the actual store front.

By the way, in creating this response I did change "1600" to "1630" and got EPE to geocode. Once I had a map, I could have followed what I did above and zoomed in until I was able to get a Street View of the actual store.

Now - about accuracy. What I like to do is to locate the coordinates of my POI files such that the coordinates are at the entrance someone would use off of a major road. Specifically, I put them such that they are within 30 meters from the approach road. Otherwise, a user will not get an "alert".

If you look at my Jo-Ann file (http://www.poi-factory.com/node/19280) you will see that I do put the coordinates of the actual store "door" in the comments field. But, I must admit that I have not actually found all of the phycical store locations (indeed, some are inside a mall and some too new to show on Street View). I know roughly where they are by calling the store and asking what entrance I would use to get to the store - but that is what I wanted to do to ensure "alerts"

WOW! now I can see the

WOW! now I can see the effort involved in maintaining/creating POI files.

I'll take the deep dive with EPE because I would want any POI file that I use to be as accurate as possible.

Thanks for all the advice!

--
“It’s their world. We’re just living in it.”

Use this to set up EPE

e_piph_a_ny wrote:

WOW! now I can see the effort involved in maintaining/creating POI files.

I'll take the deep dive with EPE because I would want any POI file that I use to be as accurate as possible.

Thanks for all the advice!

http://www.poi-factory.com/node/41653
This procedure will tell you how to setup EPE for almost any data source. It's output as a GPX will fully populate the Rand CSV format.

--
Illiterate? Write for free help.

We also rely on the users to let us know of any discrepancies.

e_piph_a_ny wrote:

WOW! now I can see the effort involved in maintaining/creating POI files.

I'll take the deep dive with EPE because I would want any POI file that I use to be as accurate as possible.

Thanks for all the advice!

--
Nuvi 2460LMT.