harvester/truck load balancing

I want to incorporate traccar into an app to monitor trucks and harvesters to load balance trucks and cutters. Is there an app to do this?

You would like to just track those machines or you are looking for app that will act as FSM app ?

I believe you are saying Field Service Management. Yes FSM is what I am looking for.
Track the harvesters (choppers, combines, etc), track the product carriers (trucks, tractors w/trailers, etc), direct enrolled carriers to enrolled harvesters to balance the load with the emphasis being keeping the harvesters running.
Allow options such as:

1. weighing the product, (both tare weight and net product) if desired.
   a. by load, field, carrier and/or harvester if desired.
   b. tare weight could be a one time carrier weight or a sample (every third load?) or every load.
2. restricting enrolled carrier assignment by field or cutter or owner as necessary.

Carriers would receive harvester ID and field ID and location when dispatched. GPS?
Carrier operators would be ID'd and tracked.

Some operations have mixed pay arrangements. Pay by tonnage harvested and/or carried, and/or paid by load harvested and/or carried.

Ex.
Cutting silage

1. The job requires 4 cutters and 12 trucks.
2. A contract harvester has two cutters and six trucks.
3. Another contract harvester has one cutter and two trucks.
4. Another contract harvester has one cutter and zero trucks.
5. Four contract truckers (maybe more) are engaged.
6. All cutters/carriers are enrolled.
   a. some restrictions are registered (field conditions, cutter capability, carrier capability, etc).
   b. field sizes, distances, restrictions are registered.
   7. App determines assignment of cutters/carriers to determine cutter/carrier quantities.
   8. App monitors conditions to maintain maximum cutter usage.
   9. App reports conditions and allows override adjustments.
7. App issues final report to allow payment for services and knowledge of the total operation condition.

There will be other issues identified but this will give an idea of the scope of the app.

Ok, so You have several options. You could use commercial product like IFS (very robust) or others available on the market.
Personally we are delivering such solutions based on odoo - so you could test such requirements on your own if it's possible.

I checked odoo. Do you have a recommendation which apps/modules to start with and/or any combination? I think I see a lot of apps that could touch on one aspect of the goal.

You may start from github.com/OCA/field-service version 16.0, you could also add maintenance module and fleet for machinery.
But there are some "issues":

1. not automatic loadbanacing is available ootb - we are creating our own module based on openstreetmaps for distance calculation.
2. interation with GPS is availabale as paid module - we will create our implementation but curently is not availabale.
3. if you are looking for dedicated mobile app there will be a gap in this area - we have created our own implementation ex.
   

Thank you for your attention and suggestions. I think I have decided to proceed with C and python.