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WARNING - TomTom's fuel POIs can disrupt the Camera warnings
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Andy_P
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PostPosted: Sun Apr 11, 2010 7:19 pm    Post subject: Reply with quote

...........

Last edited by Andy_P on Sun Apr 11, 2010 7:25 pm; edited 1 time in total
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Andy_P
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PostPosted: Sun Apr 11, 2010 7:21 pm    Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn Reply with quote

M8TJT wrote:
Even worse, they must already have the gash code do the sums on the fly in the satnav


So it's being yet another bit of pointless code SLOWING DOWN the core application! Evil or Very Mad
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AliOnHols
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PostPosted: Sun Apr 11, 2010 7:31 pm    Post subject: Reply with quote

Post deleted. Sorry M8TJT, even fewer clues!
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Last edited by AliOnHols on Sun Apr 11, 2010 7:45 pm; edited 1 time in total
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Andy_P
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PostPosted: Sun Apr 11, 2010 7:39 pm    Post subject: Reply with quote

Whoops, on reflection, I moved that post of mine over to a quieter part of the forum. No quick enough, obviously! Smile
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M8TJT
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PostPosted: Sun Apr 11, 2010 7:40 pm    Post subject: Reply with quote

I wish I knew what you are all talking about Confused Confused
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Andy_P
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PostPosted: Sun Apr 11, 2010 9:39 pm    Post subject: Reply with quote

Don't worry, nothing important. Just me going off-topic again. Wink
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BMW330
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PostPosted: Mon Apr 12, 2010 10:17 am    Post subject: Reply with quote

PaulB2005 wrote:
Please don't use asterisks to circumvent the auto censor....


Sorry, I wasn't aware of the existence of an auto-censor - I was censoring my own comment.
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BMW330
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PostPosted: Mon Apr 12, 2010 10:28 am    Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn Reply with quote

Andy_P wrote:
M8TJT wrote:
Even worse, they must already have the gash code do the sums on the fly in the satnav


So it's being yet another bit of pointless code SLOWING DOWN the core application! Evil or Very Mad


Yip, and it gets better. I've noticed that many of the websites that provide TomTom POI in the form of .ov2 files don't bother to index these downloads (NB: PGPSW is not one of these rogue sites!) - so if TT wants to know what POI are within x distance, it has to read and check every individual POI record in the whole ov2 file - imagine if that file has tens of thousands of entries in it, and if you have a number of them. An indexed ov2 file on the other hand can typically be drilled into to find the records of interest very, very efficiently with about 1-5 read operations.
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Andy_P
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PostPosted: Mon Apr 12, 2010 8:14 pm    Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn Reply with quote

BMW330 wrote:
I've noticed that many of the websites that provide TomTom POI in the form of .ov2 files don't bother to index these downloads

- so if TT wants to know what POI are within x distance, it has to read and check every individual POI record in the whole ov2 file
-
An indexed ov2 file on the other hand can typically be drilled into to find the records of interest very, very efficiently


Interesting..... I didn't know about that.

What form does this indexing take then? I thought an POI file was just a simple list of placenames, Lat/Long coordinates and an optional phone number.

BMW330 wrote:
(NB: PGPSW is not one of these rogue sites!)

So what do places like PGPSW do differently?
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Darren
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PostPosted: Mon Apr 12, 2010 10:25 pm    Post subject: Re: WARNING - TomTom's fuel POIs can disrupt the Camera warn Reply with quote

Andy_P wrote:
So what do places like PGPSW do differently?

We index our files Wink
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Andy_P
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PostPosted: Mon Apr 12, 2010 10:54 pm    Post subject: Reply with quote

So he said, but what does it involve?
Is it a header to the file or something in each record? Because all I know is each individual record uses (using the easier to read .csv version for clarity) either simple 3 column records: longitude, latitude, name

or 4 column records: longitude, latitude, name, comment

such as (some examples I stole of the net)

-110.12345,44.98765,"ACME Shoe Store","Phone: 555-829-8293"
-110.12332,44.98622,"Ace Lock Smith","24 hour service"
-110.12131,44.91422,"Public Restroom",""
-110.11932,44.95662,"Golden Kites","123 Main Street"
-110.11310,44.94222,"Public Restroom",""

What's the index do and where does it go? I'm obviously not asking Google the right questions Confused
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pcaouolte
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PostPosted: Tue Apr 13, 2010 1:05 pm    Post subject: Reply with quote

Andy,

From memory the ov2 file can contain type 1 records that define a rectangle and type 2 records that contain details of the POI's within that rectangle. There are also other record types that contain POI data but in a compressed form.

If the ov2 file contains only type 2 records the tomtom will need to search the whole file to find a POI.

If the ov2 file is "indexed" with type 1 records then the tomtom can know which rectangle is currently displayed on screen and find all POI's within the "current" rectangle (and adjacent rectangles) without searching the whole file.

To clarify (?) the ov2 file can contain:
Type 1 record: Defines area covered by whole map
Type 1 record: Defines a smaller area within map
Type 1 record: Defines yet smaller area
.... eventually
Type 1 record: Defines very small area
Then (perhaps 10) Type 2 records: Define POI's within very small area
Type 1 record: Defines another very small area
More Type 2 records within that small area.

I have more precise details of the workings of this at home if you want them.

Does that help?
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Andy_P
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PostPosted: Tue Apr 13, 2010 2:42 pm    Post subject: Reply with quote

pcaouolte wrote:


Does that help?


It certainly does, thanks Thumbs Up

So is indexing only available for .ov2 format files, or is there an equivalent for Garmin/csv and others?

And what sort of software would you need to *do* the indexing? The usual POIEdit/Tyre et.c progs don't seem to have that sort of functionality.
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pcaouolte
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PostPosted: Wed Apr 14, 2010 1:05 pm    Post subject: Reply with quote

Sorry Andy, I only have a tomtom so I haven't any info on Garmin devices.

The better quality pieces of software that create ov2 files automatically put the indexing type 1 records into the file without asking the user. I can't find any info on the POIEdit or Tyre web sites to say if they include the type 1 records or not but I would expect that they do.

To find out, you could create an ov2 file using POIEdit or Tyre and then examine the ov2 file with a hex editor. If the first byte in the file is hex 01 then the file is indexed. Any other value in the first byte and the file is not indexed. A short example of the first part of an indexed ov2 file downloaded from this site with the start of each type 1 record highlighted in red and the start of each type 2 record highlighted in blue is shown below:

01 4a 01 00 00 4c e2 ff ff f4 f5 4f 00 e7 d1 f9
ff 33 e4 4c 00 01 90 00 00 00 1a da fc ff f4 f5
4f 00 e7 d1 f9 ff 33 e4 4c 00 01 3c 00 00 00 1a
da fc ff 13 6d 4e 00 e7 d1 f9 ff 33 e4 4c 00 02
27 00 00 00 e8 d1 f9 ff 34 e4 4c 00 50 6c 79 6d
70 74 6f 6e 2c 20 44 65 6c 69 76 65 72 79 20 4f
66 66 69 63 65 00 01 3f 00 00 00 1a da fc ff f4
f5 4f 00 e7 d1 f9 ff 13 6d 4e 00 02 2a 00 00 00
73 d4 f9 ff f5 f5 4f 00 41 62 65 72 79 73 74 77
79 74 68 2c 20 44 65 6c 69 76 65 72 79 20 4f 66
66 69 63 65 00 01 a5 00 00 00 4c e2 ff ff f4 f5
4f 00 1a da fc ff 33 e4 4c 00 01 51 00 00 00 4c
e2 ff ff 13 6d 4e 00 1a da fc ff 33 e4 4c 00 .......
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