Platinum Map Programs

March 5, 2002

Hi All;

If I don't climb alot of mountains and don't fall into many valleys is there any reason why I would select the Topo map CD as opposed to the Streets and Destinations.

I will be mostly metal detecting and geocaching with travel mixed in. Live in Illinois and normally know how high I am depending on the amount that I've had.

What am I not considering and are there any other options I should be considering.

This forum was instrumental in helping me decide on the unit, now I need help on the software.

Thanks to all that help.

March 5, 2002

I have Streets & Destinations, and am quite happy with it. So far, the street accuracy is quite acceptable. Some of the POI data is off by a couple hundred yards, but is usually OK.

However, here in Florida, we have two altitudes: wet and dry. This means that ANY map that shows water is a topo map.

March 5, 2002

I wish they would combine the two, or reduce the price enough to make buying both an affordable option. I'd like to have the POI DB, but don't want to sacrifice the cool topo stuff (like elevation profile).

Dave

March 5, 2002

Get a job like me.......work in an Outdoors store. Prodeal the platinum, accesories, and software for ~60% off of retail.

March 5, 2002

Get a job like me.......work in an Outdoors store. Prodeal the platinum, accesories, and software for ~60% off of retail.

March 5, 2002

quote:
Originally posted by bozly:
Get a job like me.......work in an Outdoors store. Prodeal the platinum, accesories, and software for ~60% off of retail.

Bozly,

I have no idea what you are talking about and replies like yours are uterly useless and demeaning to this website, where people can get real constructive advice to our questions and our needs.

___ Off!

March 5, 2002

quote:
Originally posted by bozly:
Get a job like me.......work in an Outdoors store. Prodeal the platinum, accesories, and software for ~60% off of retail.

Bozly,

I have no idea what you are talking about and replies like yours are uterly useless and demeaning to this website, where people can get real constructive advice to our questions and our needs.

___ Off!

March 5, 2002

quote:
Originally posted by antheyreoff.com:
Bozly,

I have no idea what you are talking about and replies like yours are uterly useless and demeaning to this website, where people can get real constructive advice to our questions and our needs.

___ Off!

P.S.

If you want my co-ordinates I'll give them to you!

March 5, 2002

(Ah, yes, the trolls are out tonight. .)

Anyway, MapSend Topo does have POI data, in case the product sheets are confusing (What has POI? Where is the topo from? Do they all have streets? Aaaarrgh!). Anyway, Topo doesn't have as much POI data as S&D, but they have *basically* the same streets, and obviously, Topo adds the topo, which is nice.

March 5, 2002

quote:
Originally posted by ClayJar:
(Ah, yes, the trolls are out tonight.

TIA

AtP

March 5, 2002

quote:
Originally posted by ClayJar:
(Ah, yes, the trolls are out tonight.

TIA

AtP

March 5, 2002

aded map?

The detail map (i.e., the uploaded map) is shown instead of the base map when you're zoomed in. How far you have to zoom in to get the detail map depends on what you have the detail level set to in the Map Setup screen (accessible from the map screen's menu).

You can tell you're on the detail map by when city streets show up. Zoom in, and at a certain point (depending on your detail setting), all the local streets pop up. Zoom out a level and you're back on basemap.

quote:
Answers specific to the MeriPlat are appreciated since that is the unit I'm planning on getting, but general answers regarding other units would be helpful, too.

All the Meridians are the same firmware (now), so except questions relating to the thermometer, barometer, or electronic compass, the answers apply. (And of course, the MeriGreen has a small basemap, too.)

March 5, 2002

aded map?

The detail map (i.e., the uploaded map) is shown instead of the base map when you're zoomed in. How far you have to zoom in to get the detail map depends on what you have the detail level set to in the Map Setup screen (accessible from the map screen's menu).

You can tell you're on the detail map by when city streets show up. Zoom in, and at a certain point (depending on your detail setting), all the local streets pop up. Zoom out a level and you're back on basemap.

quote:
Answers specific to the MeriPlat are appreciated since that is the unit I'm planning on getting, but general answers regarding other units would be helpful, too.

All the Meridians are the same firmware (now), so except questions relating to the thermometer, barometer, or electronic compass, the answers apply. (And of course, the MeriGreen has a small basemap, too.)

March 6, 2002

Also, in case you do not know.......

The resolution of the Magellan topo is lower than the Garmin topo.

Also, if you read the review of the Magellan topo from Joe Mehafey's site, they state that the topo data is "compressed."

Because of the nature of the data, I suspect JPEG-type compression. The data is very low frequency, and this is how I would compress it. This means that you can fit a lot of topo data into very little memory.

In short, it will tell you where mountains are, but it is no substitute for a real paper map while doing serious outdoor activities (such as hunting or mountain climbing).

March 6, 2002

quote:
Originally posted by antheyreoff.com:
Bozly,

I have no idea what you are talking about and replies like yours are uterly useless and demeaning to this website, where people can get real constructive advice to our questions and our needs.

___ Off!

Much anger in you.......... You should really lay off the caffeine. You have invigorated me to post a senseless post every time you post. For Love of the game mon cheri!

Bozly

March 6, 2002

quote:
Originally posted by Harrkev:
Also, in case you do not know.......

The resolution of the Magellan topo is lower than the Garmin topo.

Also, if you read the review of the Magellan topo from Joe Mehafey's site, they state that the topo data is "compressed."

Because of the nature of the data, I suspect JPEG-type compression. The data is very low frequency, and this is how I would compress it. This means that you can fit a lot of topo data into very little memory.

In short, it will tell you where mountains are, but it is no substitute for a real paper map while doing serious outdoor activities (such as hunting or mountain climbing).

Well, in case YOU did not know, Magellan (and Garmin) receivers are using vector data for maps, POIs and such. You can't use jpg type compression for vector. jpg is for raster.

The interesting part about Magellan's topo is that it contains actual elevation information and is using that to generate elevation contour lines. The display of the contour lines may be at lower interval than on Garmin maps BUT Magellan receivers can also generate elevation profiles at much higher density. This is capability not matched by any other receivers, so far.

Saying that; I do agree that Magellan nor Garmin topo maps are NOT a substitute for a small scale, printed topo map.

March 7, 2002

Yes. Map data (streets) is in vector format. POI data is not "vector," because a vector has a beginning and an end. A POI is a 1-d point.

What you have to keep in mind is that the representation of the data is determined by the data itself. A street is very long and narrow. Therefore, it lends itself very nicely to being approximated by a vector. EVERY point on land has an elevation. This type of data is not condusive to being stored in vector format. You COULD store the actual contour lines themselved in vector format, but from what I understand, this is not done my Magellan.

If you look at elevation as being a "bitmap" (whick makes sense) then doing some type of frequency-domain compression seems logical. JPEG compression uses the DCT (discrete cosine transform), and then quantizes the DCT data. This would work wonderfully because elevation would be extremely low frequency data, so wonderful compression ratios would be easy to achieve.

And about generating more contour lines. If the original data is low-resolution, you could generate infinite contour lines, but that could not create more detail than was there originally. If you have any experience with digital cameras, take a 640x480 camera, and scale the image to 5 mega-pixels. The resulting image will look nothing like an image from a 5 mega-pixel camera. Same concept for topo data.

I am not knocking Magellan. There is always a tradeoff in detail vs. price and detail vs. memory. Had I been in their shoes, I might have made the same decision. I like their products. But you do have to understand the limitatons of their decisions.

quote:
Originally posted by gpsmapnut:
Well, in case YOU did not know, Magellan (and Garmin) receivers are using vector data for maps, POIs and such. You can't use jpg type compression for vector. jpg is for raster.

The interesting part about Magellan's topo is that it contains actual elevation information and is using that to generate elevation contour lines. The display of the contour lines may be at lower interval than on Garmin maps BUT Magellan receivers can also generate elevation profiles at much higher density. This is capability not matched by any other receivers, so far.

Saying that; I do agree that Magellan nor Garmin topo maps are NOT a substitute for a small scale, printed topo map.

[This message was edited by harrkev on March 07, 2002 at 05:31 AM.]

March 7, 2002

quote:
Originally posted by gpsmapnut:
The interesting part about Magellan's topo is that it contains actual elevation information and is using that to generate elevation contour lines.

Sorry. I don't mean to pick on you.

You CANNOT store "actual elevation information" for a large area in a vector format. The fact that the Meridian can generate the topo lines "on the fly" means that it is stored in a format similar to a bitmap.

March 8, 2002

quote:
Originally posted by ClayJar:

The detail map (i.e., the uploaded map) is shown instead of the base map when you're zoomed in. How far you have to zoom in to get the detail map depends on what you have the detail level set to in the Map Setup screen (accessible from the map screen's menu).

You can tell you're on the detail map by when city streets show up. Zoom in, and at a certain point (depending on your detail setting), all the local streets pop up. Zoom out a level and you're back on basemap.

So when zoomed in the basemap POI's will or will not be visible? IOW, if I have a MeriPlat with the Marine basemap in it and I zoom in will I still see no wake zones and/or buoys?

AtP

March 8, 2002

quote:
Originally posted by harrkev:

>snip>

Sorry. I don't mean to pick on you.

You CANNOT store "actual elevation information" for a large area in a vector format. The fact that the Meridian can generate the topo lines "on the fly" means that it is stored in a format similar to a bitmap.

Yes, you can store the actual elevation information for a large area. That’s exactly what DEMs are. Obviously, the file size is relative to the area size and data resolution resolution.

Personally, I haven’t used Garmin topos on a receiver. I just seen them on the Garmin’s website viewer and read some reports. I’m lead to believe that the contour lines are similar to the ones on 1:100.000 (or even larger scale) USGS printed maps. From what I’ve seen of it, DEM used by Magellan is of the same or better resolution. I’m not talking here real resolution NOT interpolated.

AFAIK when it comes to maps, the real distinction between vector and raster is:

Vector GIS data contain actual geospatial information. Geospatial data in vector formats may include not only vectors but also points, lines, polilynes, polygons and other geometrical entities that can be mathematically defined. They are all collectively called vector data.

Raster data contain graphical representation of geospatial information.

Because of it, POIs and waypoints are vector map data.

Not all DEMs are collections of elevation information about individual points spaced on an even grid. The ones that are could be said to represent elevation in the way that a bitmap is using to represent a picture. You assume that Magellan used such a DEM,but it's only an assuption.

Also; they could’ve used a number of compression algorithms. Some are loosless, some are not.

Saying that possibly Magellan used JPEG-type compression implies compression that reduces data quality. I haven’t seen anything that would indicate such compression used in this case.

I may be overreacting a bit to use of jpg / bitmap analogy with vector GIS data; but I see a constant stream of “how can I load xxx (whatever raster map) to xxx (whatever GPSR)” and similar questions that are directly related to not knowing the distinction between raster and vector maps.

Andrew Kalinowski

www.GPSNuts.com Recreational GPS and mapping (hobby)

www.CanadianMaps.ca Raster topo (and some other) maps

March 8, 2002

quote:
Originally posted by gpsmapnut:

Because of it, POIs and waypoints are vector map data.

How can a single point be a vector?

Respectfully,

AtP

March 8, 2002

quote:
Originally posted by gpsmapnut:

Because of it, POIs and waypoints are vector map data.

How can a single point be a vector?

Respectfully,

AtP

March 8, 2002

A point is a vector with no magnitude.

quote:
Originally posted by Atilla the Pun:

How can a single point be a vector?

Respectfully,

AtP

March 8, 2002

A point is a vector with no magnitude.

quote:
Originally posted by Atilla the Pun:

How can a single point be a vector?

Respectfully,

AtP

March 8, 2002

quote:
Originally posted by Atilla the Pun:

quote:
_Originally posted by gpsmapnut:_

Because of it, POIs and waypoints are vector map data.

How can a single point be a vector?

Respectfully,

AtP

Sorry to confuse you. ;-) In what I typed, there is one sentence which was out of place:

"Raster data contain graphical representation of geospatial information." Should be the last in the paragraph and the sentence you are refering to should be second last.

I'll try to edit that post to fix that.

Andrew Kalinowski

www.GPSNuts.com Recreational GPS and mapping (hobby)

www.CanadianMaps.ca Raster topo (and some other) maps

March 8, 2002

quote:
Originally posted by Atilla the Pun:

quote:
_Originally posted by gpsmapnut:_

Because of it, POIs and waypoints are vector map data.

How can a single point be a vector?

Respectfully,

AtP

Sorry to confuse you. ;-) In what I typed, there is one sentence which was out of place:

"Raster data contain graphical representation of geospatial information." Should be the last in the paragraph and the sentence you are refering to should be second last.

I'll try to edit that post to fix that.

Andrew Kalinowski

www.GPSNuts.com Recreational GPS and mapping (hobby)

www.CanadianMaps.ca Raster topo (and some other) maps

March 8, 2002

quote:
Originally posted by infosponge:
A point is a vector with no magnitude.

Ok, I'll grant you that, but then there's no "data compression" in that sort of a vector.

AtP

March 8, 2002

quote:
>snip>

point

>snip>

Ok, I'll grant you that, but then there's no "data compression" in that sort of a vector.

AtP

It may not be efficient to compress data for individual points. OTOH it may be feasible to compress database consisting of points.

Do you use zip files? Most of the ones that contain information about points zip very nicely ?

In case of vector maps / data that are loaded to the receiver, I doubt that any compression is used. Naturally, that may depend on definition of compression. To me (YMMV) compression implies that the data is decompressed before used. I think that the data is stored on the receiver in a proprietary format that allows the unit software to access it directly.

As long as after decompression all the information is the same as before the compression, it makes no diff to me. All it does is reduces memory required at a cost of processing cycles used for decompression.

Andrew Kalinowski

www.GPSNuts.com Recreational GPS and mapping (hobby)

www.CanadianMaps.ca Raster topo (and some other) maps

March 8, 2002

GPSmapnut. I cannot quote your previous long message, as the "reply" feature of this board appears to not work for me.

Yes, any vector data can have other attributes, such as elevation associated with it. However, suppose that you are in the woods away from any roads or POI or other data usually associated with "vector" data... Then, where do you get your data from???

A vector, at a minimum, has an X and Y coordinate. These coordinates take space to store. This would be the only way to store data if your original source was a group of irregularly-spaced points. Now, let's assume that that you have regular data. A much more efficient method of data storage would be a matrix. This is similar to a bit-map, except that each "pixel" represents a height instead of a brightness value. This type of low-frequency data can also be compress readily.

If your height data really is irregularly-spaced data, then interpolation becomes a problem. You are then faced with making choices like interpolating using weighted averagine or gaussian estimation. I would not want to have to determine how to interpolate this data. Not a fun job.

Below is a quote directly from Joe Mehaffey's web site (he is well-respected)

*** BEGIN QUOTE ***

Background:

The source of Magellan topo maps are USGS 1 dg DEM (Digital Elevation Model) data. Here altitudes are recorded at the vertices of the 3 sec x 3 sec (grid) that covers all CONUS. This is about 90m x 90m cells. A similar linear resolution grid covers Alaska. Magellan has developed proprietary compression algorithms that allowed it to convert 2.758 Gbytes of original US DEM data into 72.7 Mbytes. Magellan has compressed data that can be uncompressed on the fly in a unit. Alaska adds another 29.4Mbytes compressed out of the original 1.238 Gbytes Alaska DEM data. Magellan reports that the compression is done with no more than 3 m RMS error and with no more than 10 m max error of compression.

*** END QUOTE ***

Aparently, they use a grid, and they have slightly lossy compression. At a superficial level, this sounds exactly like a B/W JPEG file. I would not be surprised if they used similar techniques. You let your data itself determine how best to store it.

March 9, 2002

OK, so as Joe wrote, the source data for elevations in Magellan was a typical DEM which is a matrix. Even that it makes it very similar in the way it stores information about the points to the way bitmap stores information about a picture, from GIS perspective it is still vector data. It is so because for each point in the matrix, the geographical information is given.

You wrote: "A vector, at a minimum, has an X and Y coordinate." Yes, this is true for A vector. To make it map vector data, these have to be geographical coordinates and have to be associated with a map feature. in DEM, the coordinates of each point are stored in a matrix.

It really makes no difference how the coordinates for each point are stored - whether they are derived from a matrix, given individually for each point or in a series where coordinates of a fist point are given and subsequent points are defined by offset from the first point or by any mix of the above. I've seen them all being used. What's more; even that Garmin is not using DEM in their topos, the map they load to their receiver is still vector, not raster. Once again; this is so because the data loaded to the receiver has information about the geographical location of the map features. This data is used to render the map on the receiver's screen.

The real difference between the elevation information used and ultimately displayed to the user by Garmin is two dimensional. It contains no actual elevation information. It is information that tells the receiver where to draw contour lines on the map screen. Viewing the contours lines on the screen, you may be able to interpret the display and figure out elevation for each place on the display. Not any different than looking at a printed map. You can't place the cursor some place on the map and have the unit tell you the elevation value for that point. You can't create a route and have the report the elevation profile across the route, you can't pick a road segment and display its' vertical profile. All you can do is to point to the contour line and have the associated label displayed.

In Magellan, you can do this because the data is there.

I know and respect Joe. We had many battles and even more friendly discussions over the years.

In the review, you are referring to (http://www.gpsinformation.net/exe/maptech/mag-topo.html ) Joe compared elevations reported by Magellan's topo to USGS 7.5' topo maps and concluded that "… the accuracy is pretty good". In the samples he has taken, the largest error is 6 meters.

Garmin elevation contours, depending on the area, are at 10 to 40 meters (elevation difference) interval.

Does it mean that Magellans elevation is more accurate than Garmins? There is no simple answer to that. For some areas one and for some areas the other will be more accurate.

In your post you wrote: "suppose that you are in the woods away from any roads or POI or other data usually associated with "vector" data... Then, where do you get your data from???"

Well, I'm not sure what are you getting at there, but to answer your question:

Assuming that you are asking about the map data, not current,.

On Magellan, where available (=USA) I could (I'm Canadian) get the elevation information by setting one of the data fields to elevation. Simple activating the map cursor (just a tap on the cursor pad) would change the elevation display from GPS computed 3D position to the elevation computed from DEM data for the cursor position. With Garmin, I would have to zoom out until elevation contours are visible, point to couple of them and mentally deduct my elevation.

To get idea about my location on the map, regardless of the receiver used, I would have to zoom out until enough features is displayed on the screen to visually "place myself on the map". If I needed greater accuracy, I would plot my co-ordinates on a printed map. If I wanted a good overview of my location, but not needed my precise location, I would estimate my position in relation to the features visible on the screen (zoom out as necessary) and than related that to a printed map.

If… than I'd use one of the thousand ways to skin the cat

BTW. I also have problems to reply with quotes on this forum. Funny thing is, I don't know how to reply without!!! So, I'm using reply with quotes and deleting the quotes. Frequently; "reply with quotes" kicks me out to the main forum menu. If it happens, I use "back" in my browser (IE) and try again and again and again. On one of the tries, it finally works…

Gosh, I just posted miles of text and realised that I have not commented on:

" Aparently, they use a grid, and they have slightly lossy compression. At a superficial level, this sounds exactly like a B/W JPEG file. I would not be surprised if they used similar techniques. You let your data itself determine how best to store it."

Since you said: "At a superficial level", I have no option but to agree with you Still, I don't exclude possibility that they used fractals in the algorithm. After all, vector mapping is more of a geometry than visual art.

Andrew Kalinowski

www.GPSNuts.com Recreational GPS and mapping (hobby)

www.CanadianMaps.ca Raster topo (and some other) maps

[This message was edited by gpsmapnut on March 09, 2002 at 07:06 AM.]

March 9, 2002