Method of labelling a highly curved path on a map rendered on a wireless communications device
View Patent ↗In displaying a map on a wireless communications device, a method is provided that resolves labelling of sharp curves. The method entails a determination of whether a curvature of a map element associated with the map feature exceeds a predetermined threshold (e.g. whether a rate of change in slope of a path or the change in angular orientation of each successive character in the label exceeds a threshold that is a function of zoom level. If the curvature exceeds the threshold, the label is rendered on the map in a new map location that avoids the map location where the curvature exceeds the threshold.
1. A method of displaying a map on a wireless communications device, the method comprising steps of:
obtaining map data for rendering the map to be displayed on the wireless communications device, the map data including label data for rendering a label for identifying a map feature on the map;
determining whether a curvature of a map element associated with the map feature exceeds a predetermined threshold; and
rendering the label on the map in a new map location that avoids the map location where the curvature exceeds the predetermined threshold.
2. The method as claimed in claim 1 wherein the step of determining whether the curvature exceeds the predetermined threshold comprises a step of determining a rate of change in slope
∂
2
y
∂
x
2
of a map feature at the map location where the label is to be rendered.
3. The method as claimed in claim 2 wherein the predetermined threshold varies as a function of a zoom level of the map.
4. The method as claimed in claim 2 further comprising steps of:
generating a collision-avoidance array representative of the map to be rendered for testing potential label positions prior to actually rendering the labels on the map; and
populating the collision-avoidance array by designating one or more undesirable locations in the array corresponding to map locations on the map where the curvature exceeds the predetermined threshold.
5. The method as claimed in claim 1 wherein the step of determining whether the curvature exceeds the predetermined threshold comprises a step of determining a rate of change in slope
∂
2
y
∂
x
2
of a path at the map location where the label is to be rendered.
6. The method as claimed in claim 5 wherein the predetermined threshold varies as a function of a zoom level of the map.
7. The method as claimed in claim 1 wherein the step of determining whether the curvature exceeds the predetermined threshold comprises steps of:
virtually rendering the label along its respective path by provisionally orienting each character of the label; and
determining whether a change in angular orientation of each character in the label relative to its preceding character in the label exceeds a predetermined angular threshold.
8. The method as claimed in claim 7 wherein the predetermined threshold varies as a function of a zoom level of the map.
9. The method as claimed in claim 7 further comprising steps of:
generating a collision-avoidance array representative of the map to be rendered for testing potential label positions prior to actually rendering the labels on the map; and
populating the collision-avoidance array by designating one or more undesirable locations in the array corresponding to map locations on the map where the curvature exceeds the predetermined threshold.
10. The method as claimed in claim 7 further comprising steps of:
generating a collision-avoidance array representative of the map to be rendered for testing potential label positions prior to actually rendering the labels on the map; and
populating the collision-avoidance array by designating one or more undesirable locations in the array corresponding to map locations on the map where the curvature exceeds the predetermined threshold.
11. The method as claimed in claim 1 wherein the predetermined threshold varies as a function of a zoom level of the map.
12. The method as claimed in claim 1 further comprising steps of:
generating a collision-avoidance array representative of the map to be rendered for testing potential label positions prior to actually rendering the labels on the map; and
populating the collision-avoidance array by designating one or more undesirable locations in the array corresponding to map locations on the map where the curvature exceeds the predetermined threshold.
13. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 1 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
14. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 2 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
15. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 3 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
16. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 4 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
17. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 5 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
18. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 6 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
19. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 7 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
20. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 8 when the computer readable medium is loaded into memory and executed on a processor of a-wireless communications device.
21. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 9 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
22. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 10 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
23. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 11 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
24. A non-transitory computer readable medium comprising code adapted to perform the steps of claim 12 when the computer readable medium is loaded into memory and executed on a processor of a wireless communications device.
25. A wireless communications device for enabling a user of the device to display a map on the device, the wireless device comprising:
an input device for enabling the user to cause the device to obtain map data for rendering the map to be displayed on a display of the device, the map data including label data for rendering labels on the map for identifying one or more map features; and
a memory for storing code to instruct a processor to:
obtain map data for rendering the map to be displayed on the wireless communications device, the map data including label data for rendering a label for identifying a map feature on the map;
determine whether a curvature of a map element associated with the map feature exceeds a predetermined threshold; and
render the label on the map in a new map location that avoids the map location where the curvature exceeds the predetermined threshold.
26. The wireless communications device as claimed in claim 25 wherein the processor determines a rate of change in slope
∂
2
y
∂
x
2
of a map feature at the map location where the label is to be rendered.
27. The wireless communications device as claimed in claim 25 wherein the processor determines a rate of change in slope
∂
2
y
∂
x
2
of a path at the map location where the label is to be rendered.
28. The wireless communications device as claimed in claim 25 wherein the processor virtually renders the label along its respective path by provisionally orienting each character of the label and then determines whether a change in angular orientation of each character in the label relative to its preceding character in the label exceeds a predetermined angular threshold.
29. The wireless communications device as claimed in claim 25 wherein the predetermined threshold varies as a function of a zoom level of the map.
30. The wireless communications device as claimed in claim 25 wherein the processor generates a collision-avoidance array representative of the map to be rendered for testing potential label positions prior to actually rendering the labels on the map and then populates the collision-avoidance array by designating one or more undesirable locations in the array corresponding to map locations on the map where the curvature exceeds the predetermined threshold.