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Locus Map - help desk Topic Question Locus Map (Android)

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Category Locus Map (Android)

Application Locus Map 4

Comments 23

Subscribers 5

Votes 2

LiDAR- Digital Terrain Models (DTM) as ZIP possible ?

freischneider shared this question ago

Answered

The DTM files are stored in the SRTM folder. Can these also be saved as ZIP ? Or do I have to unzip them all and it takes less space.

The same question

Replies (13)

Michael Bechtold ●

Locus does need the hgts as files, not embedded in a ZIP as far as I know.

In the end, ZIP files are useless anyway, because the hgt is needed on the fly - and as FAAAST as possible. Ergo: no ZIP, because expanding takes time and battery - times 10 or 100s, depending on the size of the area you are researching.

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freischneider ●

Thanks, time and battery are 2 good arguments. Then it is also advantageous to store it internally and not on the external SD ?
How does it look with Theme. They are automatically stored as ZIP. Is time and battery there no argument ?

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Michael Bechtold ●

It is - BUT :-))

- ZIPed themes were a remedy against the issues that came with Google's insane storage access restrictions (tons of SVG files on EXT SD e.g. are a nightmare).

- when Menion implemented the ZIP theme feature, his approach was to take the themes ZIP and create a hidden copy in internal menory

- result: stability re. permission/EXT SD perf issues, plus high performance

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freischneider ●

I have everything on the internal SD since the permissions issues. I have enough storage space. Currently only the themes are as ZIP. Since it is so created by OAM. Externally I have only pictures from the camera and the backup from Locus.

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Andrew Heard ●

I have Sonny's ZIPs, 1 per .hgt file in /data/srtm, and it works for me. I've not noticed any change of device speed. They must be working as I use them for the offline LM4 Route Planner.

A large saving in each file size, for example N51W008.zip = 201KB, N51W008.hgt = 25,327KB.

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Michael Bechtold ●

Very interesting, hence I immediately did a test:

1) zipped a hgt file into the srtm folder

2) deleted the hgt file

3) started Locus, dynamic elevation activated

4) rather than using the zip file, Locus downloaded the missing hgt file ...

What is the difference between our Locus?

Cheers

Michael

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Andrew Heard ●

I don't believe it's a caching issue. My SRTM folder contains all the Sonny ZIP files for Ireland. It never contained the raw .HTG files. Menion may care to confirm whether .ZIP is supported.

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Mick FU ●

I did same test and it doesn't work for me neither with full France (only zip from Sonny, 1'', and no hgt). Dynamic elevation is not displayed.

It would have been very nice indeed

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Michael Bechtold ●

@Menion: can you please advice?

Thank you and cheers Michael

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Menion ●

Hi guys,

there is probably some magic on the Andrew side, because zipped SRTM files are not supported 😊. Interesting idea. We will probably discuss native support for download 1'' files soon and here zipped files may help. But it will be necessary to work in similar way as map themes (as mentioned by Michael) > a lot of extraction to private directory.

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Michael Bechtold ●

PS: and when you extract to private directory, the space explosion will happen there, in particular for the 1" variant.

In other words: there is no magic at hand at all.

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Michael Bechtold ●

PPS: the ZIP approach would ease one problem, though: exploding download volumes (for the 1" ones) by the Locus internal automatic download from your servers.

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Menion ●

Yes, that is correct. And mainly during shading in the higher zoom, this may cause a massive slowdown ...

Not ideal ... sorry.

So, this feature is not supported and I currently do not see any major benefit to doing it (sure, except saved space).

PPS: data are of course already downloaded compressed.

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Andrew Heard ●

Weird - what magic would that be/ what more can I check? I have again checked tablet & phone - both currently only have 24 x *.ZIP (Sonny's Ireland) + WW15MGH.DAC in locus/data/srtm. I've also done a Solid Explorer search for *.HGT with no results. My test is to create a short route with the route planner then check the elevation profile - which looks reasonable, and LM4 does not complain of missing data files.

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Mick FU ●

Andrew, are you talking about elevation in route planners?

And we are speaking about dynamic elevation display on the map dynamically.

I tried without hgt, and no dynamic altitude, but route planning is calculated with altitudes.

Difference may be there.

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Andrew Heard ●

@Mick FU - yes, elevation in route planner.

>Difference may be there.

yes, maybe

so where does elevation for the Route Planner come from? if not from HGT, then RD5 file(s)? surely more than just dynamic elevation display?

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Menion ●

Elevation in route planner computed by the BRouter or LoRouter does not need an offline elevation data. The router already includes these data inside (based on 3`` HGT files!

Simply try to "Update elevation" on any saved route ...

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Andrew Heard ●

>Simply try to "Update elevation" on any saved route

yup - failed - requires download, sorry for any confusion

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Andrew Heard ●

So to take advantage of higher resolution HGT files, I first have to use the Route Planner (but only 3" data), then save the track, then re-open from the Track list > More > Tools > Update Elevation. That's confusing, and why I assumed the ZIP files were working, when actually ignored.

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Michael Bechtold ●

Menion, who is producing the rd5 files, the BRouter team, or your's?

In any case, using sonny's 1" LIDAR files for Europe should not kill the processing speed for their creation, right?

Cheers

Michael

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Menion ●

@Andrew Heard

confusing, well. BRouter needs elevation data to correctly compute routes, times etc. So elevation values are already included in the generated route and it was logical not to waste power to compute these values again.

Anyway, as Michael mentioned, using 1'' would not have an effect on the generation speed. It is just some work on our side. Anyway, we had a meeting yesterday where we planned tasks till the end of this year and better work with 1'' data (so it's usage for the router and also an option to download them directly over the app) is definitely planned soon.

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Sonny ●

In Locus classic v3 the behaviour of using Route Planner is the following:

The rough BRouter elevation values are just used if there is no .hgt file of the region in Locus' SRTM-folder.

If there is a .hgt file (1" or 3"), Locus automatically uses this file for calculation elevation sums. So no need to execute an extra "Update elevation"

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Andrew Heard ●

@Sonny - seems more logical from a user's point of view. I had downloaded your 1' ZIPs thinking I was getting more accurate slope data for an upcoming cycle tour, whereas in fact the more accurate elevations were completely ignored.

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