I would prefer that my RPF layer transition from JNC ONC as soon as there is
enough ONC data to fill the screen. Currently, I have to zoom in much
farther than necessary before the ONC connects. I even start noticing the
differences between JNC and VMAP level 0 before the transition to ONC
occurs. If the transition occurs sooner, then I don't believe the user will
notice the JNC/VMAP difference. The ONC and VMAP are a much closer match, as
we might expect.
-----Original Message-----
From: Don Dietrick [mailto:dietrick_at_bbn.com]
Sent: Monday, December 19, 2005 1:07 PM
To: Klawetter, DG Darol (6274) _at_ IS
Cc: 'openmap-users_at_bbn.com'
Subject: Re: [OpenMap Users] RPF and VMAP Descrepancy
I didn't notice a big discrepancy when viewed a 1:1M for the other
borders that would be defined by coordinates. There were a couple
that seemed a couple of pixels off, but in general they seem pretty
close to the ONC. The coastlines in N/S Carolina seem right on.
I suppose this could be a display problem, if OpenMap were rendering
some of the borders as great circle lines instead of rhumb lines, but
I'd expect that the vmap polygon points are close enough together to
make that irrelevant.
On Dec 19, 2005, at 12:53 PM, Klawetter, DG Darol (6274) _at_ IS wrote:
> The VMAP was made from the ONC, so shouldn't the borders be a copy
> of the
> ONC? I undertand your point about the interpreting of river paths,
> but there
> are differences along borders that are artificial (e.g. Oklahoma &
> Kansas).
>
> -----Original Message-----
> From: Don Dietrick [mailto:dietrick_at_bbn.com]
> Sent: Monday, December 19, 2005 11:40 AM
> To: Klawetter, DG Darol (6274) _at_ IS
> Cc: 'openmap-users_at_bbn.com'
> Subject: Re: [OpenMap Users] RPF and VMAP Descrepancy
>
>
> 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 Tue Dec 20 2005 - 12:48:50 EST