David,
What may seem at first glance to be a simple feature request actually
involves much more strategic and long term issues......
MapInfo is at present primarily meant to be a vector GIS package, and
therefore it's forte is in manipulating and analyzing vector data. The
ability to "warp" raster images is a significant programmatic endeavor that
would require an extensive development commitment on MapInfo's part, made
doubly difficult due to the fact that MapInfo has relatively little
experience in manipulating raster data formats. The ability to warp images
in a cartographically correct way is a science and an industry all its own.
The software products that can do this (ERDAS, ER Mapper, to name a few)
have spent many years perfecting this technology, and have made it the focus
of their business. Conversely, the ability to re-project vector data to
overlay on top of an image is a relatively simple task for a vector mapping
package such as MapInfo that already has a built in capability to define
custom projections. If MapInfo were to add image warping capability, I
believe it would signify a significant and strategic change in product
direction, and would drastically reduce the development resources left over
for the myriad other enhancements this list has been clamoring for. In
short, I do not believe that MapInfo does things "backwards", rather it is
acting according to it's true nature - a born and bred vector GIS package.
As a side note, in regards to whether vector data is "better" than
raster data, there are some caveats to consider. First, when working in a
mapping environment, aerial imagery needs to be orthorectified. This takes
care of the "stretch", "skew", and even to varying degrees the topographical
distortion. If an image is not orthorectified then it does not matter
whether the vectors are fit to the image or vice-versa; the result would be
unsuitable for most mapping purposes.
Most orthorectified images that I've come across are at least accurate
to 1:24,000 NMAS if not better. Comparatively, most widely available vector
street data, such as TIGER and GDT/BLR/MapInfo streets, are only accurate to
1:100,000 NMAS. (With the exception of ETAK, which is 1:24,000 in metro
areas) This means that in most cases orthorectified raster data is more
accurate than vector data that covers the same area. However, if you have
digitized in your own vector data to more accurate standards then this
obviously is not always the case.
Hope this has helped,
Chris
Christopher DuBuc
Applications Engineer
[EMAIL PROTECTED]
www.mapfactory.com
----- Original Message -----
From: David Baker <[EMAIL PROTECTED]>
To: MapInfo-L (E-mail) <[EMAIL PROTECTED]>
Sent: Monday, May 17, 1999 9:30 AM
Subject: RE: MI Adding raster image rotates map!
> On 17 May 99, at 18:31, Perry Chris wrote:
>
> > MapInfo skews and rotates vectors (lines, points, polygons) to match
> > registered images.
>
> Does this seem backwards to anyone else? Most people are going to have
good vector information, but
> less people are going to have "good" raster information - there is always
going to be some angular error in
> aerial photography, or stretch or skew in scanned images, so it's very
unlikely the raster data will be
> "better" than the vector data....
>
> Thanks for the pointers from people regarding software that works the
correct way - I'll check them out.
> Hopefully future versions of MapInfo (if I can afford them) will allow my
maps to stay where they are without
> trying to rotate them!
>
> Dave
> --
> ------------------------------------------------------
> | David Baker | [EMAIL PROTECTED] |
> | Electronics Engineer | Kuala Lumpur, Malaysia |
> |----------------------------------------------------|
> | http://www.geocities.com/SiliconValley/Vista/8552/ |
> ------------------------------------------------------
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