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TOPIC: Insight Map Creator Issue

Insight Map Creator Issue 5 years 4 months ago #7251

  • rsbyers84
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I have been trying to create ArcGIS Imagery maps for my Lowrance HDS units...the process that have taken is as follows:
1. Download tiles from SAS.Planet
2. Export KML file with ArcGIS Imagery overlay
3. Start IMC and begin with Keyhole mode
4. Open file with KML file from SAS.Planet
5. Build
6. Upon completion, swap over to Raster mode
7. Open cashe file from SAS.Planet folder for zoom desired
8. Designate destination folder for Bound AT5's
9. Build

As I go through this process, everything seems to work out just fine (aside from taking a long time to build) until I start building in Raster mode....it will build these large maps and at some point, it will stop the process and give an error message..."write size did not meet expected write size"...this ends the process and I have to start over.

Can you help explain what I may be doing wrong to cause this error message?
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Insight Map Creator Issue 5 years 4 months ago #7252

  • gpiverson
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This is a generic error. What it literally means is that the data stream attempted to write some information and how many bytes the data stream was told to write was not the same as the number of bytes it did write which is considered a critical error by the Insight Map Creator.

This can mean a lot of things. It might mean that you were attempting to write to a location that you did not have access to at your current rights (like C:\Program Files, C:\Windows, a locked SD card). It might mean that you ran out of space on that drive. It usually doesn't mean that anything logically messed up in the process.
Last Edit: 5 years 4 months ago by gpiverson.
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Insight Map Creator Issue 5 years 4 months ago #7254

  • rsbyers84
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My destination "write" folder is on a 32GB zip drive...it has plenty of room available. Knowing that, would you still think I could be having the same issues?
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Insight Map Creator Issue 5 years 4 months ago #7259

  • Matt
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rsbyers84 wrote:
My destination "write" folder is on a 32GB zip drive...it has plenty of room available. Knowing that, would you still think I could be having the same issues?

One thing that would definitely be worth trying is exporting to your hard drive first -choose a folder somewhere where you know you have a lot of space. The IMC creates a lot of temporary files during the generate so perhaps there is some issue here with exporting directly to the SD card?
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Insight Map Creator Issue 5 years 4 months ago #7261

  • gpiverson
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Matt wrote:
The IMC creates a lot of temporary files during the generate so perhaps there is some issue here with exporting directly to the SD card?

The space required for temporary files on the raster process is as large as the final outputted dataset.

If the application fails well into processing, I would suspect the issue is likely the min resolution being set way too low for the dataset.
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Insight Map Creator Issue 5 years 4 months ago #7294

  • longjohn119
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Building to a USB or SD card isn't a good idea because of the way solid state memory works. When they are building a map they are writing and then deleting and writing and deleting lots of files. When you delete a file only the header is actually erased. However you cannot just overwrite old data like a hard disk drive, the sectors have to be erased first. IMC and other programs (audio and video editors) that write and rewrite a lot of data often don't even try to erase sectors they still consider them written data and eventually the drive fills up and you get an I/O error because there is no longer any free AND erased sectors left. Sometimes the programs do try to erase sectors but that creates a bottleneck and again an I/O error.

You could have the same problems if you tried to do something like this on an Android, Apple, and most Windows tablets. Benchmark disk speeds on a Windows tablet and a Windows laptop with a real Solid State Drive and even if they have the same processor and RAM the laptop is going to eat that tablet's lunch in read and especially write speeds. A big part of the difference is having a dedicated RAM buffer to hold data when there is a bottleneck writing to the drive (Actually the bottleneck is from erasing sectors first).
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Insight Map Creator Issue 5 years 4 months ago #7296

  • gpiverson
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Almost all Windows programs do not directly delete files on the hard drive. They either directly use Windows API calls or use a wrapper that uses Windows API calls. The IMC is no exception. It's built on top of the Qt SDK which wraps low level functions.

While it's true that the sector needs to be erased before it is rewritten to on a SSD, the erasing is usually handled by TRIM on modern versions of Windows. In cases where it isn't, the erasing is done before it's written to. While this slows down performance, it won't cause an I/O error from time out.
Last Edit: 5 years 4 months ago by gpiverson.
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