Re: [OpenMap Users] RPF and VMAP Descrepancy

From: Don Dietrick <dietrick_at_bbn.com>
Date: Mon, 19 Dec 2005 12:40:04 -0500

Hi Darol,

I think you can chalk this discrepancy up to cartographic license and
time. Since that border is a river, it probably depends on when the
RPF was made and when the VMAP was made, and how the cartographer
interpreted the river markings when the VMAP was made. I've checked
the VMAP against several different levels of CADRG, and none of them
match exactly for the data I have, and all CADRG levels portray a
different river path as well. It's generally the same, but not exact.

- Don

On Dec 19, 2005, at 10:35 AM, Klawetter, DG Darol (6274) _at_ IS wrote:

> Here's the screenshot.
>
> -----Original Message-----
> From: Klawetter, DG Darol (6274) _at_ IS
> Sent: Monday, December 19, 2005 9:34 AM
> To: 'Don Dietrick'
> Cc: openmap-users_at_bbn.com
> Subject: RE: [OpenMap Users] RPF and VMAP Descrepancy
>
>
> Thanks for responding. I'm comparing VMAP Level 0 to ONC CADRG
> data. I've
> attached a screenshot of a portion of the Texas/Oklahoma border
> that shows
> the descrepancy (notice my Az/Rng marker). I believe that this
> difference
> could be due to our paper maps being at JNC (1:2M) instead of ONC
> resolution
> (1:1M). I'm trying to get some ONC data right now so that I can
> compare.
>
> -----Original Message-----
> From: Don Dietrick [mailto:dietrick_at_bbn.com]
> Sent: Saturday, December 17, 2005 8:12 PM
> To: Klawetter, DG Darol (6274) _at_ IS
> Cc: openmap-users_at_bbn.com
> Subject: Re: [OpenMap Users] RPF and VMAP Descrepancy
>
>
> Hi Darol,
>
> What level of VMAP and RPF are you comparing against each other? I
> think Level 0 VMAP was made from ONC CADRG data (1:1000000), so if
> you compare it to JGA or TLM data, I'd expect the RPF to be correct,
> and the VMAP data to be exceeding the precision of the source data.
> I've not seen an error that large, though.
>
> If you are looking at the VMAP browse level coverage, I think that
> data is in a different datum, so you will see it off by a bit. It's
> better to use the cntry02 data that's in the latest version of
> OpenMap.
>
> - Don
>
>
> On Dec 16, 2005, at 5:55 PM, Klawetter, DG Darol (6274) _at_ IS wrote:
>
>> I've noticed that when displaying RPF and VMap data, the political
>> borders
>> as shown by the VMap political boundary layer do not match the
>> borders as
>> shown by the RPF paper maps. Sometimes the difference is as great
>> as 1 arc
>> minute. Why am I seeing this difference? The users of my map don't
>> know
>> which boundaries are correct.
>>
>> Thanks,
>>
>> Darol
>>
>> --
>> [To unsubscribe to this list send an email to "majdart_at_bbn.com"
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>
> <tx_ok_border.gif>

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Received on Mon Dec 19 2005 - 12:40:58 EST

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