Note 8 - Rental Equipment - Rental Equipment (Details) - Equipment [Member] - USD ($) $ in Thousands	Jun. 30, 2025	Sep. 30, 2024
Rental equipment, primarily wireless recording equipment	$ 48,571	$ 63,111
Accumulated depreciation	(38,250)	(48,925)
Property, Plant, and Equipment, Lessor Asset under Lease, after Accumulated Depreciation	$ 10,321	$ 14,186

Amount, before accumulated depreciation, of lessor's underlying asset for which right to use has been conveyed to lessee under lease.

No definition available.

Name:	geos_PropertyPlantAndEquipmentLessorAssetUnderLeaseBeforeAccumulatedDepreciation
Namespace Prefix:	geos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant