Managing Multiple surveys in the same cave

[Stelios Zacharias]

Dear Marco, 

I manage the data for the Sternes expedition on Crete. 

This is a multi-year expedition that has miltiple survey teams working at the same time in different parts of the cave, since 2023 we have been entirely paperless using TopoDroid.

Before 2023 we have paper-based surveys dating from 2017-2022. 

I use the project feature to tie all the individual surveys together. 

When moving from year to year (for example 2025 to 2026), I will export all the 2025 surveys into vTopo compile them as one file, and then will import the resulting .tro into TopoDroid as a base for the 2026 surveys. I then create a new project, using the imported 2025 base and adding the 2026 surveys to that as they come in. 

The alternative would mean having to share to everyone doing the survey in 2026 all the individual surveys done the year(s) before, and then to also explain how to link togehter the individual surveys to create the correct project file for the new year. 

My main question is do we lose fidelity when exporting / importing to vTopo, and are the magnetic North data conserved? When exporting to .tro format are the data adjusted for magnetic variance already, risking double adjustment if it is done also in vTopo? 

Is there a workflow that you as designer have in mind as being an optimum for our situation? Basically, this last question is the most important. 

Many thanks for your time.

Cheers, 
Stelios Zacharias

     

[Marco Corvi]

On Fri, Aug 7, 2026, 11:48 Stelios Zacharias <i.can.sk...@gmail.com> wrote:

Dear Marco, 

I manage the data for the Sternes expedition on Crete. 

This is a multi-year expedition that has miltiple survey teams working at the same time in different parts of the cave, since 2023 we have been entirely paperless using TopoDroid.

Before 2023 we have paper-based surveys dating from 2017-2022. 

I use the project feature to tie all the individual surveys together. 

When moving from year to year (for example 2025 to 2026), I will export all the 2025 surveys into vTopo compile them as one file, and then will import the resulting .tro into TopoDroid as a base for the 2026 surveys. I then create a new project, using the imported 2025 base and adding the 2026 surveys to that as they come in.

how do you cope with magnetic declination changing over the years ?

The alternative would mean having to share to everyone doing the survey in 2026 all the individual surveys done the year(s) before, and then to also explain how to link togehter the individual surveys to create the correct project file for the new year. 

My main question is do we lose fidelity when exporting / importing to vTopo, and are the magnetic North data conserved?

topodroid tries to read the declination from tro/trox file. if reading fails, it records a log statement - general users do not look at logs, so this is a silent failure.

by inspecting the code it seems that, if read, the declination is applied to the input data. 

When exporting to .tro format are the data adjusted for magnetic variance already, risking double adjustment if it is done also in vTopo?

vtopo export does not adjust the data for the magnetic declination.

the declination is not save to the tro/trox file.

maybe vtopo uses the data and the location to compute the declination and adjust the data.

Is there a workflow that you as designer have in mind as being an optimum for our situation? Basically, this last question is the most important.

have a look at at CaveArchive.

it might be useful for your situation.

Many thanks for your time.

Cheers, 
Stelios Zacharias

     

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[Stelios Zacharias]

On Fri, Aug 7, 2026 at 1:10 PM Marco Corvi <marco...@gmail.com> wrote:

On Fri, Aug 7, 2026, 11:48 Stelios Zacharias <i.can.sk...@gmail.com> wrote:

Dear Marco, 

I manage the data for the Sternes expedition on Crete. 

This is a multi-year expedition that has miltiple survey teams working at the same time in different parts of the cave, since 2023 we have been entirely paperless using TopoDroid.

Before 2023 we have paper-based surveys dating from 2017-2022. 

I use the project feature to tie all the individual surveys together. 

When moving from year to year (for example 2025 to 2026), I will export all the 2025 surveys into vTopo compile them as one file, and then will import the resulting .tro into TopoDroid as a base for the 2026 surveys. I then create a new project, using the imported 2025 base and adding the 2026 surveys to that as they come in.

how do you cope with magnetic declination changing over the years ?

I guess topodroid makes it calculations on the basis of the dates and location of the survey legs. 

vTopo has a calibration function where it takes the declinations from the date and location again. 

 

The alternative would mean having to share to everyone doing the survey in 2026 all the individual surveys done the year(s) before, and then to also explain how to link togehter the individual surveys to create the correct project file for the new year. 

My main question is do we lose fidelity when exporting / importing to vTopo, and are the magnetic North data conserved?

topodroid tries to read the declination from tro/trox file. if reading fails, it records a log statement - general users do not look at logs, so this is a silent failure.

by inspecting the code it seems that, if read, the declination is applied to the input data. 

When exporting to .tro format are the data adjusted for magnetic variance already, risking double adjustment if it is done also in vTopo?

vtopo export does not adjust the data for the magnetic declination.

the declination is not save to the tro/trox file.

maybe vtopo uses the data and the location to compute the declination and adjust the data.

 

So - when importing again, it loses magnetic variance data because the timing of the survey leg does not survive the journey to vTopo and back. This is not yet significant as over 10 years it is about 0.5 degrees, which even for a 2 km underground stream is only 17m - not even 1%. 

 

 

Is there a workflow that you as designer have in mind as being an optimum for our situation? Basically, this last question is the most important.

have a look at at CaveArchive.

it might be useful for your situation.

I will look into this - thank you. 

Stelios

 

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