Mbtiles

[avant]

I’m experimenting with mbtiles, and wonder if there is any input from those in the know on what parameters one should stay within for success.

Area covered, detail levels, file sizes, etc. — do any of these affect performance, response time in the app, etc.?

Thanks all

[conachair]

http://www.cruisersforum.com/forums/...ml#post2860707

[yachtvalhalla]

Originally Posted by avant

I’m experimenting with mbtiles, and wonder if there is any input from those in the know on what parameters one should stay within for success.

Area covered, detail levels, file sizes, etc. — do any of these affect performance, response time in the app, etc.?

Thanks all

Why not use Sat2Chart to make the Mbtiles? DownloadÂ*


Terry

[avant]

Thanks Terry

Regardless of how one makes the ‘charts’, are there parameters one should stay within?

You could make one mbtiles file of the whole coast of North America, for example. Would that be ok performance wise, or should one do smaller areas to cover a large area like that?

I’m wondering what the implications are for memory management, graphics display, etc. Are within the app.

Rob on Avant

[avant]

Terry, I did try sat2chart for making mbtiles, but found it wasn’t really any easier than just using sasplanet directly (actually, I found it harder!). I’m a keen user and big fan of ge2kap, and have been for years, but I just wasn’t seeing much value add in using sat2chart for mbtiles.

Rob on Avant

[yachtvalhalla]

Originally Posted by avant

Thanks Terry
Regardless of how one makes the ‘charts’, are there parameters one should stay within?
You could make one mbtiles file of the whole coast of North America, for example. Would that be ok performance wise, or should one do smaller areas to cover a large area like that?
I’m wondering what the implications are for memory management, graphics display, etc. Are within the app.
Rob on Avant

Hi Rob,

I presume the 'app' you refer to is OpenCPN. I can't speak to that issue specifically but can tell you that I've made charts of the coastlines of major islands in the Philippines and also for coastlines in Indonesia, Taiwan and Borneo. These are displayed by OpenCPN without any problem. And for utility I do them at a low enough zoom level to see the reefs and shoals that usually are not displayed on the basic navigation chart. Bear in mind I do this for these poorly charted regions in Asia. We don't have the luxury of NOAA charts out here.



It's in the creation of the charts that you need to take in small bites. I found that 50-100 NM to be a limiting length due to the coverage available from the various sources - Google Earth, Yandex, Nokia, Bing, and ESRI/ArcGIS as available from the SASPlanet website. You will find that cloud coverage varies between the sources and it's a matter of selecting the best one .. and often not known until after the chart has been made and viewed. If unacceptable then I create another chart of the same area using the best coverage. To do this for a very long 'bite' can be time consuming and tiresome.


HTH, Terry

[avant]

Thanks Terry

I’m cruising in Latin/Central America and suffer from poor charts as well. I’ve been grabbing ~75-100 miles at a time. Which gives ~100,000 mbtiles files at zoom level 18, fantastic detail and seemingly good response time in use, with ‘tolerable’ waits for downloads and mbtiles creation. Clouds aren’t much of a problem in the google maps images here, and I’m using sat2chart with google earth with google’s ‘historical images’ view turned on to find clearer images as required and mixing them with the mbtiles to get a clear view of obscured features in the current google maps view. This gives the added bonus of a ‘date stamp’ on the kap image.

I’m loving the new feature. Mbtiles are delivering clearer images and more detail with less work than the GE2KAP process allowed.

I do wish I understood what triggers the display of mbtiles better, and the implications of multiple charts in memory management in the OpenCPN app better.

Rob on Avant.

[Capt.Don]

I experimented with different regions in individual MBTILE files. I ended up creating geographically distinct cruising regions in large MBTILE files (SCal, Sea of Cortez, Mexico). For example, using the Sea of Cortez as an example, rather than having "baja-pacific", "baja-soc", "mexico-soc", ...., I ended up with a single MBTILE for all of Baja, Sea of Cortez. This ends up being a huge file (~7GB).

One of the problems when using multiple MBTILE files, when there's overlap regions OpenCPN displays the outlines for the overlap. Each MBTILE is a separate "chart". Focus and zoom in the overlapping area was odd. You have to deselect one or the other MBTILEs. This is documented behavior, though I found this to be a bit clumsy.

Regarding a single file, I've found OpenCPN's performance to be fine. MBTILEs store all the chart meta-data and chart image in a SQL database. Databases are optimized to find records. In this case, based on the display area, fetch and show all the charts. OpenCPN w/SQL database does a great job of retrieving chart data. Compare this to 1,000's of KAP files on your computer. OpenCPN has to open each file, fetch the chart data and image, etc. Although OpenCPN preprocesses this in its own internal database, I think MBTILES is just as good if not better.

I also stopped using GE2KAP (SAT2KAP) and use SASPlanet directly. The advantage is SASPlanet stores the individual Google Earth graphic image tiles, while GE2KAP takes a screen print from your monitor. The MBTILE images are full color and resolution. When displaying an area, SASPlanet combines all the little downloaded tiles for display. The combined image is then stored in the output MBTILE.

Using SASPlanet, I used Bing Maps. To make the MBTILE, I created polygon regions at different zoom levels. I used Z8 for the entire area, Z11, Z13, Z15 for cruising area and Z18 for coastal/anchorage. All these are combined when exporting to the MBTILE. When using OpenCPN, I'll see "Over Zoom" as it zooms in/out between the different zoom levels. Note, SASPlanet stores all the little tiles on your computer under the "cache" folder. You'll see the folders for different sources, zoom levels, then files for sets of tiles. I have limited disk space on my laptop, so I had to be clever on copying/backing up the SASPlanet cache folders.

One problem with very large MBTILE files is you can't easily share with other cruisers. Without physically sharing the file using a USB flash drive, it is very hard to upload/download 7GB files!

I think MBTILEs are great and I can't wait to get back to the boat and start using them for our continued cruising adventure!
Don

[avant]

Thanks Don.

I don’t think I have the patience (or perhaps the computer) to generate a 7gb mbtiles file!

Nice to hear it works though.

Rob on Avant

[Capt.Don]

Rob,

With SASPlanet, it is not that hard. Simply create polygon regions by clicking points along the coast, then let SASPlanet spend days downloading the tiles. I just let my laptop work away and every few days I'd start another zoom level download. I like the functionality and chart resolution in OpenCPN w/MBTILEs -- definitely worth the effort. Last season, we visited 50+ anchorages. The images were a necessary supplement to the cruising guides. I wouldn't want to approach a new anchorage without OpenCPN and satellite charts.

A single 7GB file is a lot easier to manage than 1,000's of individual KAP files in folders I probably could cut the size considerably by only including high-level zooms (Z18) for the popular anchorages (instead of the entire coast). Probably also don't need all the Z11-Z13-Z15's levels either. It was easier just to let SASPlanet download everything and not worry about missing something.

Give it a try -- you won't be disappointed!
Don

[rgleason]

Are there any suggestions for this section with regard to mbtiles and sas handling with Chart Files and Chart Tabs?

Use Chart Groups and Chart Files


If good example screenshots are uploaded here, I can include one or two.


If someone wants to make a good page on MBtiles I can start the page and set you up as a manager/editor.

[rgleason]

OpenCPN is opensource and is a volunteer army. Users are expected to help in the ways they can, by reporting bugs in tracker, discussing improvements, and editing and improving the documentation in the wiki. Without user help there would be no wiki. Users play a vital role in support and documentation of OpenCPN.

The OpenCPN Manual (wiki) now has a page under Charts regarding the use of "MBtiles & Other Formats".

It is just an outline right now. Please contribute text and screenshots in this thread for this wiki page. Also provide any suggestions you wish regarding changes/corrections/improvements. Other users depend on your contributions.

Several users who are familiar with the use of MBtiles and willing to contribute, should be made Manageer/Editors. PM me if you are interested. Thank you.

[phiggins]

Capt Don you said:

I also stopped using GE2KAP (SAT2KAP) and use SASPlanet directly. The advantage is SASPlanet stores the individual Google Earth graphic image tiles, while GE2KAP takes a screen print from your monitor.

That is absolutely false. When creating mbtiles charts from SasPlanet Sat2Chart invokes the downloads and export on Sasplanet. No screenshots! In other words it creats the same mbtiles that you would doing the whole thing manually.

Also Sat2Chart allows you now to create Mbtiles charts from Google earth will no loss of color.