Note 18 - Supplemental Cash Flow Information - Supplemental Cash Flow Information Components (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Cash paid for income taxes	$ 151	$ 169
Non-cash investing and financing activities:
Inventory transferred to rental equipment	587	1,148
Inventory transferred to property, plant and equipment	0	172
Issuance of notes receivables related to sale of used rental equipment	$ 0	$ 11,745

Represents the amount of inventory transferred to rental equipment.

No definition available.

Name:	geos_InventoriesTransferredToRentalEquipment
Namespace Prefix:	geos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of inventory transferred to property, plant, and equipment.

+ References

No definition available.

+ Details

Name:	geos_InventoryTransferredToPropertyPlantAndEquipment
Namespace Prefix:	geos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Issuance Of Notes Receivables In Connection With Sale Of Used Rental Equipment.

+ References

No definition available.

+ Details

Name:	geos_IssuanceOfNotesReceivablesInConnectionWithSaleOfUsedRentalEquipment
Namespace Prefix:	geos_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482913/230-10-50-2

+ Details

Name:	us-gaap_IncomeTaxesPaidNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration