As a new field of visualization

knowledge visualization is to use maps

graphics

or images to construct and transfer insights and knowledge between at least two persons.In view of geovisualization

geographic diagram

geo-informatic Tupu

and visual analytics are cutting edge researches on visual and graphic representation and discovery of geographic knowledge.Thus

this paper focuses on the discussion of geographic knowledge visualization in terms of general knowledge visualization and geographic diagram.In the paper

the concept and characteristics of knowledge maps in geographic knowledge visualization are mainly explored according to the dual coding theory of representation of mental images

features of geospatial thinking

and need for supporting visual exploration of geo-knowledge.Geo-knowledge maps are defined as cognitive and abstract maps related to geo-problems

geographic spatiotemporal distribution

relationship of geographic factors

and so on.They should be fit for mental image representation and cognitive process

and helpful for human spatial memory

thinking and imagination to improve capability to handle geo-problems.Considering images like digital photos and remote sensing images

they all mimic the physical world in real life without any abstract contents of human thinking and reasoning.Therefore

this paper defines these mimic images as geo-information images which have differences from geo-knowledge maps that express human knowledge about the real world.Geo-knowledge maps have two kinds: weak and strong.Weak geo-knowledge maps have more objective

concrete

and mimic description

while strong maps are more subjective and abstract.Geo-knowledge maps have two classes: concept propositional maps and analogue diagrammatic maps.Concept propositional maps highlight verbal handling of geographic phenomena

while analogue diagrammatic maps represent geographic graphics and images.With regard to analogue diagrammatic maps

there are further four types: logic and topological similar maps

spatial structure similar maps

variable-relationship similar maps

and process similar maps.As a case study

a few of practical knowledge maps for supporting spatial planning of dam systems in watersheds are presented.