MapForums

Hello,

I'd like to know why the latitude and longitude I get in MapPoint 2004 is not equal to the MapPoint 2002.


Thanks,
Jc.

Hi Jc.

How big of a difference are you seeing and what are the specific locations/addresses?

I think it may arise from at least three general and related issues.

1.) Difference in geocode quality. Whereas for a street segment MapPoint 2002 may not have had an address range and it geocoded to the centroid of the street segment, MapPoint 2004 may now have the range and it geocodes more precisely. Note this can also go in the other direction, for a specific street segment, MapPoint 2004 may have lost the address range.

2. ) Shifting streets. This refers not to geomorphological and tectonic activity, but rather the street data vendors may get the roads more accurately digitized and in line with actual GPS readings.

3. ) Change in data vendor for an area. Microsoft uses a couple different data vendors and then makes a "cut" or merge of the two data sources and uses each where it is most accurate. The data vendors being used for a specific street or area may have changed between the two versions.

hope this helps!
Eric

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For example, Belfast:
MapPoint 2002 ==> lat: 54,5938290244 lon: -5,9231089043
MapPoint 2004 ==> lat: 54,5958052984 lon: -5,9354862631

We have a database with these values (latitude, longitude to every city). If we change the version, we'll have problems because we are using these fields as keys (we can not use the name as key because there are localities with the same name in the same province).

Will the coordinates change in the next version? and the names of the localities?

One question more, with MapPoint 2002 we have more localities than MapPoint 2004, why?


Thank you ver much,
Jc.

Hi Jc.

You really should not use lat/lon as a key.. it's subject to rounding error, truncation, etc. Also, as cities expand and municipal boundaries shift, the centroid would be different. Also, there may be arguments to use the commercial center of a town as opposed to the geographic center.

I don't know anything about your app, but I would recommend trying to use something other than lat/lon as the key. If you really have to, you could code a quickie straight line distance calculation using some trig in VB or C if you're confident the locality will still be the closest one. Hope that makes sense.

One question more, with MapPoint 2002 we have more localities than MapPoint 2004, why?

I imagine they changed the data provider for Ireland?

Honestly if you're just looking at things at the level of "locality" and the old version has more.. there may be no compelling reason to upgrade? It may be a different story if you are doing street routing, not sure.

Eric

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Another possible source of error is the buggy grid reference calculation in MapPoint 2002 which is fixed in 2004. This would only have an effect if data was loaded into MapPoint using the grid references. My experience for the mainland (Wales and Yorkshire) suggests that the road database was loaded without using grid references. (fixed coordinates match roads/etc better than the originals).

re. Ireland: Yes I've heard this complaint quite a bit. I think Microsoft did change the data providers for the European edition. Other countries also suffered but I seen more complaints for Eire.
I was under the impression that Northern Ireland was okay, but perhaps it does come under the same provider.


Richard

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