public Sector getBBox() {
    if (null != this.coverage) return this.coverage;

    this.coverage = Sector.EMPTY_SECTOR;
    MapSource myMapSource = this.mapSource;
    for (Iterator<MapSource> iterator = myMapSource.getChildren(); iterator.hasNext(); ) {
      MapSource ms = iterator.next();
      try {
        MapGenerator gen = (null != ms) ? ms.getMapGenerator() : null;
        if (null != gen) {
          Sector bbox = gen.getBBox();
          if (null != bbox) this.coverage = Sector.union(this.coverage, bbox);
        }
      } catch (Exception e) {
        Logging.logger()
            .severe(
                "CompoundImageryGenerator:getBBox: undefined coverage of child map source"
                    + ms.getName());
      }
    }
    return this.coverage;
  }
    public ImageFormatter serviceRequest(IMapRequest req) throws IOException, WMSServiceException {
      int reqWidth = 512;
      int reqHeight = 512;

      this.threadId = Thread.currentThread().getId();

      MapSource myMapSource = CompoundImageryGenerator.this.mapSource;
      Logging.logger()
          .info("START CompoundServiceInstance :: serviceRequest( " + myMapSource.getName() + ")");
      try {
        Integer bgColor = CompoundImageryGenerator.DEFAULT_MISSING_DATA_COLOR;
        String bgColorStr = req.getBGColor();
        if (bgColorStr != null && 0 < bgColorStr.length()) {
          try {
            bgColor = Integer.parseInt(bgColorStr, 16);
          } catch (NumberFormatException ex) {
            Logging.logger()
                .severe("Unable to parse BGCOLOR in get imagery request: " + ex.getMessage());
            bgColor = CompoundImageryGenerator.DEFAULT_MISSING_DATA_COLOR;
          }
        } else
          Logging.logger()
              .severe(
                  "BGCOLOR was not specified in the getImagery request: using default " + bgColor);

        req.setBGColor(bgColor.toString());

        reqWidth = (req.getWidth() > 0) ? req.getWidth() : 512;
        req.setWidth(reqWidth);

        reqHeight = (req.getHeight() > 0) ? req.getHeight() : 512;
        req.setHeight(reqHeight);

        Sector reqSector =
            Sector.fromDegrees(
                req.getBBoxYMin(), req.getBBoxYMax(), req.getBBoxXMin(), req.getBBoxXMax());

        double reqPixelSize = reqSector.getDeltaLatDegrees() / reqHeight;
        MapSource reqMapSource = null;

        for (Iterator<MapSource> iterator = myMapSource.getChildren(); iterator.hasNext(); ) {
          MapSource ms = iterator.next();
          MapGenerator gen = (null != ms) ? ms.getMapGenerator() : null;
          if (null == gen) {
            Logging.logger()
                .severe("child mapSource `" + ms.getName() + "` has no associated map generator!");
            continue;
          }
          Sector bbox = gen.getBBox();
          Logging.logger()
              .info(
                  "found child mapSource `" + ms.getName() + "` with generator: " + gen.toString());
          if (!reqSector.intersects(bbox)) {
            Logging.logger()
                .info(
                    "child mapSource`"
                        + ms.getName()
                        + "`: out of coverage, skipping"
                        + bbox.toString());
            continue;
          }

          double genPixelSize = gen.getPixelSize();
          reqMapSource =
              ms; // assumes layers are configured in order according to resolutions from low to
          // high
          Logging.logger()
              .info(
                  "Comparing texel sizes: req = "
                      + reqPixelSize
                      + " , layer's = "
                      + gen.getPixelSize());
          if (reqPixelSize >= genPixelSize) {
            // satisfactory generator found
            break;
          }
        }

        ImageFormatter fmt = null;
        if (null != reqMapSource) {
          try {
            MapGenerator gen = reqMapSource.getMapGenerator();
            Logging.logger()
                .info(
                    "`"
                        + reqMapSource.getName()
                        + "` is executing request; req texel size = "
                        + reqPixelSize
                        + " where layer's texel size = "
                        + gen.getPixelSize());
            fmt = gen.getServiceInstance().serviceRequest(req);
          } catch (Exception ex) {
            Logging.logger().severe("Error while accessing a child mapSource: " + ex.getMessage());
          }
        }

        if (null == fmt) {
          Logging.logger().info("CompoundImageryGenerator will return an empty transparent image");
          fmt = createEmptyImage(req.getWidth(), req.getHeight(), new Color(bgColor));
        }
        return fmt;
      } catch (Exception ex) {
        String msg = Logging.getMessage("WMS.RequestFailed", ex.getMessage());
        Logging.logger().log(java.util.logging.Level.SEVERE, msg, ex);
        throw new WMSServiceException(msg);
      }
    }