Abstract:
A method of creating an image file and a digital camera for the same. The method comprised the steps of: (i) generating and storing image data corresponding to a photo or video clip; (ii) sampling received GPS signals and storing the resultant GPS signal samples (hereafter “raw GPS data”); and (iii) creating a single file containing both the image data and the raw GPS data.

Description:
The present patent application is a Utility claiming the benefit of Application No. PCT/IB2007/050418, filed Feb. 8, 2007. 
     FIELD OF THE INVENTION 
     This invention relates to a method of creating an image file and a digital camera for the same. cl BACKGROUND 
     It is known to provide a digital camera having a GPS receiver wherein image files generated by the digital camera are annotated or labelled with data identifying the position of the camera at the time of capture as determined by the GPS receiver. For example, see U.S. Pat. No. 6,269,446 or European patent application EP1189021A1. 
     PCT published patent application WO2004/090903A1 discloses a method of appending a position stamp to an image file of a photo or video clip taken with a digital camera having a GPS antenna and a GPS RF front-end including an analogue to digital converter for receiving GPS signals and outputting GPS signal samples. The method comprising the steps of: (i) upon a user taking a photo or video clip: (a) creating an image file containing that photo or video clip, and (b) sampling received GPS signals and storing those GPS signal samples with an indication of the image file of the photo or video clip to which those GPS signal samples pertain; and (ii) subsequently processing the GPS signal samples to obtain a position fix and appending the position fix to the image file. 
     The inventors of WO2004/090903A1 realised that storing GPS signal samples with an indication of the image file of the photo or video clip to which those GPS signal samples pertain enables those GPS signal samples to be processed at leisure to determine a position fix and, thereafter, append a position stamp to the image file. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a method of creating an image file and a digital camera for the same. The method comprises the steps of: (i) generating and storing image data corresponding to a photo or video clip; (ii) sampling received GPS signals and storing the resultant GPS signal samples (hereafter “raw GPS data”); and (iii) creating a single file containing both the image data and the raw GPS data. 
     The present invention has all the benefits of the arrangement of WO2004/090903A1 but with simplified file handling because of the combined image data and raw GPS data in a single file. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The present invention will now be described, by way of example only, with reference to the accompanying FIGURE which shows, schematically, a PC connected to a digital camera including GPS receiver device, both operating in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the accompanying FIGURE, the PC is connected via a USB PC port and corresponding cable to a digital camera  10  which comprises a GPS front-end receiver (Rx) connected to a GPS antenna, an image sensor (IS) and memory (Mem), all under the control of a micro-controller μC. 
     When operative, the GPS receiver receives NAVSTAR SPS GPS signals through its antenna and pre-process them, typically by passive bandpass filtering in order to minimise out-of-band RF interference, preamplification, down conversion to an intermediate frequency (IF) and analogue to digital conversion. The IF signal remains modulated, still containing all the information from the available satellites. The resultant GPS signal samples are then stored in the memory (Mem). 
     In accordance with the present invention, the digital camera and PC may generate a position stamped image file as illustrated in any of the following example scenarios: 
     EXAMPLE 1 
     Upon a user in possession of the camera taking a photo, an image file containing that photo is created and stored in the memory. At the same time, the GPS receiver receives and samples GPS signals and stores the resultant GPS signal samples in memory prior to appending this raw GPS data to the image file. Typically, such raw GPS data might be in the order of 200 kB. 
     It would of course be desirable to implement the present invention with present day digital image standards. Specifically in relation to the “Exchangeable image file format for digital still cameras: Exif Version 2.2” established by Standard of Japan Electronics and Information Technology Industries Association (JEITA CP-3451), to accommodate several hundred kilobytes of data, one could place the raw GPS data in a data field of unspecified length. For example, referring to the GPS Attribute Information in table 12 of the Exif Version 2.2 standard, one could use the GPSSatellites, GPS MapDatum, GPSProcessingMethod or GPSAreaInformation fields (the latter two being of currently unspecified data type), all of which are off unspecified length. Alternatively, a non-GPS related field could be used. Perhaps in a later version of the EXIF standard, a dedicated data field could be provided. 
     Such data could also be superimposed on the image, e.g. as a new lower layer of spatial encoding although it is noteworthy that the pseudorandom nature of the data means that such data might be lost were it subjected to lossy compression. But the method would be of use if the image was not subjected to further compression (e.g. flagged accordingly until the GPS data had been processed) or used in a format in which lossless compression was subsequently applied. 
     Once the user returns home and connects the digital camera to the user&#39;s home PC, the image file with corresponding GPS signal samples is uploaded to the PC. The GPS signal samples are copied from the image file and then processed using appropriate PC based GPS signal processing software and the PCs more powerful processor to recover pseudorange information from which the position of the digital camera when the corresponding photo was taken can be determined using conventional navigation algorithms. Such GPS signal acquisition and pseudorange processing is well known, for example, see GPS Principles and Applications (Editor, Kaplan) ISBN 0-89006-793-7 Artech House. 
     Upon successfully determining a position fix, the raw GPS data can be removed from the file and the file position stamped with the determined GPS position fix. 
     EXAMPLE 2 
     As example 1 except that the image file may be created at the same time with the raw GPS data. 
     Whilst the invention has been described in the context of NAVSTAR GPS, the all weather, spaced based navigation system developed and currently operated by the US Department of Defense, it will be appreciated that the invention is equally applicable to other global positioning systems including GLONASS and Galileo and hybrids thereof. 
     Finally, from a reading of the present disclosure, other modifications will be apparent to persons skilled in the arts of GPS and digital cameras which may involve features which are already known in the design, manufacture and use of GPS receivers, digital cameras and component parts thereof and which may be used instead of or in addition to features already described herein.