Note 7 - Rental Equipment - Rental Equipment (Details) - Equipment [Member] - USD ($) $ in Thousands	Jun. 30, 2026	Sep. 30, 2025
Rental equipment, primarily wireless recording equipment	$ 42,095	$ 45,289
Accumulated depreciation	(37,535)	(37,169)
Property, Plant, and Equipment, Lessor Asset under Lease, after Accumulated Depreciation	$ 4,560	$ 8,120

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