diff --git a/doc/svg/ptraccel-trackpoint.svg b/doc/svg/ptraccel-trackpoint.svg
index 47078733..59eec520 100644
--- a/doc/svg/ptraccel-trackpoint.svg
+++ b/doc/svg/ptraccel-trackpoint.svg
@@ -77,33 +77,23 @@
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='black'  d='M141.9,422.4 L141.9,413.4 M141.9,16.7 L141.9,25.7  '/>	<g transform="translate(141.9,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
-		<text><tspan font-family="Arial" > 0.0005</tspan></text>
-	</g>
-</g>
-<g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='black'  d='M228.5,422.4 L228.5,413.4 M228.5,16.7 L228.5,25.7  '/>	<g transform="translate(228.5,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
-		<text><tspan font-family="Arial" > 0.001</tspan></text>
+	<path stroke='black'  d='M185.2,422.4 L185.2,413.4 M185.2,16.7 L185.2,25.7  '/>	<g transform="translate(185.2,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
+		<text><tspan font-family="Arial" > 5</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 	<path stroke='black'  d='M315.2,422.4 L315.2,413.4 M315.2,16.7 L315.2,25.7  '/>	<g transform="translate(315.2,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
-		<text><tspan font-family="Arial" > 0.0015</tspan></text>
+		<text><tspan font-family="Arial" > 10</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='black'  d='M401.8,422.4 L401.8,413.4 M401.8,16.7 L401.8,25.7  '/>	<g transform="translate(401.8,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
-		<text><tspan font-family="Arial" > 0.002</tspan></text>
-	</g>
-</g>
-<g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='black'  d='M488.4,422.4 L488.4,413.4 M488.4,16.7 L488.4,25.7  '/>	<g transform="translate(488.4,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
-		<text><tspan font-family="Arial" > 0.0025</tspan></text>
+	<path stroke='black'  d='M445.1,422.4 L445.1,413.4 M445.1,16.7 L445.1,25.7  '/>	<g transform="translate(445.1,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
+		<text><tspan font-family="Arial" > 15</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 	<path stroke='black'  d='M575.0,422.4 L575.0,413.4 M575.0,16.7 L575.0,25.7  '/>	<g transform="translate(575.0,444.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
-		<text><tspan font-family="Arial" > 0.003</tspan></text>
+		<text><tspan font-family="Arial" > 20</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
@@ -117,48 +107,139 @@
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 	<g transform="translate(315.1,471.3)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="middle">
-		<text><tspan font-family="Arial" >speed in units/us</tspan></text>
+		<text><tspan font-family="Arial" >delta (units)</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 </g>
-	<g id="gnuplot_plot_1" ><title>linear (mouse)</title>
+	<g id="gnuplot_plot_1" ><title>-1</title>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 	<g transform="translate(507.9,38.6)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="end">
-		<text><tspan font-family="Arial" >linear (mouse)</tspan></text>
+		<text><tspan font-family="Arial" >-1</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='rgb(148,   0, 211)'  d='M516.2,34.7 L558.4,34.7 M55.3,398.1 L575.0,398.0  '/></g>
+	<path stroke='rgb(148,   0, 211)'  d='M516.2,34.7 L558.4,34.7 M55.3,422.4 L60.5,418.5 L65.7,414.6 L70.9,410.7 L76.1,406.8 L81.3,402.9
+		L86.5,399.0 L91.7,395.1 L96.9,391.2 L102.1,387.3 L107.3,383.5 L112.5,379.6 L117.7,375.7 L122.9,371.8
+		L128.1,367.9 L133.3,364.0 L138.5,360.1 L143.6,356.2 L148.8,352.3 L154.0,348.4 L159.2,344.5 L164.4,340.6
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+		L211.2,310.0 L216.4,310.0 L221.6,310.0 L226.8,310.0 L232.0,310.0 L237.2,310.0 L242.4,310.0 L247.6,310.0
+		L252.8,310.0 L258.0,310.0 L263.2,310.0 L268.4,310.0 L273.6,310.0 L278.8,310.0 L284.0,310.0 L289.2,310.0
+		L294.4,310.0 L299.6,310.0 L304.8,310.0 L310.0,310.0 L315.2,310.0 L320.3,310.0 L325.5,310.0 L330.7,310.0
+		L335.9,310.0 L341.1,310.0 L346.3,310.0 L351.5,310.0 L356.7,310.0 L361.9,310.0 L367.1,310.0 L372.3,310.0
+		L377.5,310.0 L382.7,310.0 L387.9,310.0 L393.1,310.0 L398.3,310.0 L403.5,310.0 L408.7,310.0 L413.9,310.0
+		L419.1,310.0 L424.3,310.0 L429.5,310.0 L434.7,310.0 L439.9,310.0 L445.1,310.0 L450.3,310.0 L455.5,310.0
+		L460.7,310.0 L465.9,310.0 L471.1,310.0 L476.3,310.0 L481.5,310.0 L486.7,310.0 L491.8,310.0 L497.0,310.0
+		L502.2,310.0 L507.4,310.0 L512.6,310.0 L517.8,310.0 L523.0,310.0 L528.2,310.0 L533.4,310.0 L538.6,310.0
+		L543.8,310.0 L549.0,310.0 L554.2,310.0 L559.4,310.0 L564.6,310.0 L569.8,310.0 L575.0,310.0  '/></g>
 	</g>
-	<g id="gnuplot_plot_2" ><title>const accel 1</title>
+	<g id="gnuplot_plot_2" ><title>-0.75</title>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 	<g transform="translate(507.9,56.6)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="end">
-		<text><tspan font-family="Arial" >const accel 1</tspan></text>
+		<text><tspan font-family="Arial" >-0.75</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='rgb(  0, 158, 115)'  d='M516.2,52.7 L558.4,52.7 M55.3,422.4 L575.0,422.1  '/></g>
+	<path stroke='rgb(  0, 158, 115)'  d='M516.2,52.7 L558.4,52.7 M55.3,422.4 L60.5,415.3 L65.7,408.1 L70.9,401.0 L76.1,393.8 L81.3,386.7
+		L86.5,379.6 L91.7,372.4 L96.9,365.3 L102.1,358.1 L107.3,351.0 L112.5,343.9 L117.7,336.7 L122.9,329.6
+		L128.1,322.4 L133.3,315.3 L138.5,308.2 L143.6,301.0 L148.8,293.9 L154.0,286.7 L159.2,279.6 L164.4,272.5
+		L169.6,270.7 L174.8,270.7 L180.0,270.7 L185.2,270.7 L190.4,270.7 L195.6,270.7 L200.8,270.7 L206.0,270.7
+		L211.2,270.7 L216.4,270.7 L221.6,270.7 L226.8,270.7 L232.0,270.7 L237.2,270.7 L242.4,270.7 L247.6,270.7
+		L252.8,270.7 L258.0,270.7 L263.2,270.7 L268.4,270.7 L273.6,270.7 L278.8,270.7 L284.0,270.7 L289.2,270.7
+		L294.4,270.7 L299.6,270.7 L304.8,270.7 L310.0,270.7 L315.2,270.7 L320.3,270.7 L325.5,270.7 L330.7,270.7
+		L335.9,270.7 L341.1,270.7 L346.3,270.7 L351.5,270.7 L356.7,270.7 L361.9,270.7 L367.1,270.7 L372.3,270.7
+		L377.5,270.7 L382.7,270.7 L387.9,270.7 L393.1,270.7 L398.3,270.7 L403.5,270.7 L408.7,270.7 L413.9,270.7
+		L419.1,270.7 L424.3,270.7 L429.5,270.7 L434.7,270.7 L439.9,270.7 L445.1,270.7 L450.3,270.7 L455.5,270.7
+		L460.7,270.7 L465.9,270.7 L471.1,270.7 L476.3,270.7 L481.5,270.7 L486.7,270.7 L491.8,270.7 L497.0,270.7
+		L502.2,270.7 L507.4,270.7 L512.6,270.7 L517.8,270.7 L523.0,270.7 L528.2,270.7 L533.4,270.7 L538.6,270.7
+		L543.8,270.7 L549.0,270.7 L554.2,270.7 L559.4,270.7 L564.6,270.7 L569.8,270.7 L575.0,270.7  '/></g>
 	</g>
-	<g id="gnuplot_plot_3" ><title>const accel 2</title>
+	<g id="gnuplot_plot_3" ><title>-0.5</title>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 	<g transform="translate(507.9,74.6)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="end">
-		<text><tspan font-family="Arial" >const accel 2</tspan></text>
+		<text><tspan font-family="Arial" >-0.5</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='rgb( 86, 180, 233)'  d='M516.2,70.7 L558.4,70.7 M55.3,422.4 L575.0,422.1  '/></g>
+	<path stroke='rgb( 86, 180, 233)'  d='M516.2,70.7 L558.4,70.7 M55.3,422.4 L60.5,412.0 L65.7,401.6 L70.9,391.2 L76.1,380.9 L81.3,370.5
+		L86.5,360.1 L91.7,349.7 L96.9,339.3 L102.1,328.9 L107.3,318.5 L112.5,308.2 L117.7,297.8 L122.9,287.4
+		L128.1,277.0 L133.3,266.6 L138.5,256.2 L143.6,245.8 L148.8,235.5 L154.0,225.1 L159.2,217.6 L164.4,217.6
+		L169.6,217.6 L174.8,217.6 L180.0,217.6 L185.2,217.6 L190.4,217.6 L195.6,217.6 L200.8,217.6 L206.0,217.6
+		L211.2,217.6 L216.4,217.6 L221.6,217.6 L226.8,217.6 L232.0,217.6 L237.2,217.6 L242.4,217.6 L247.6,217.6
+		L252.8,217.6 L258.0,217.6 L263.2,217.6 L268.4,217.6 L273.6,217.6 L278.8,217.6 L284.0,217.6 L289.2,217.6
+		L294.4,217.6 L299.6,217.6 L304.8,217.6 L310.0,217.6 L315.2,217.6 L320.3,217.6 L325.5,217.6 L330.7,217.6
+		L335.9,217.6 L341.1,217.6 L346.3,217.6 L351.5,217.6 L356.7,217.6 L361.9,217.6 L367.1,217.6 L372.3,217.6
+		L377.5,217.6 L382.7,217.6 L387.9,217.6 L393.1,217.6 L398.3,217.6 L403.5,217.6 L408.7,217.6 L413.9,217.6
+		L419.1,217.6 L424.3,217.6 L429.5,217.6 L434.7,217.6 L439.9,217.6 L445.1,217.6 L450.3,217.6 L455.5,217.6
+		L460.7,217.6 L465.9,217.6 L471.1,217.6 L476.3,217.6 L481.5,217.6 L486.7,217.6 L491.8,217.6 L497.0,217.6
+		L502.2,217.6 L507.4,217.6 L512.6,217.6 L517.8,217.6 L523.0,217.6 L528.2,217.6 L533.4,217.6 L538.6,217.6
+		L543.8,217.6 L549.0,217.6 L554.2,217.6 L559.4,217.6 L564.6,217.6 L569.8,217.6 L575.0,217.6  '/></g>
 	</g>
-	<g id="gnuplot_plot_4" ><title>const accel 3</title>
+	<g id="gnuplot_plot_4" ><title>-0.25</title>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
 	<g transform="translate(507.9,92.6)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="end">
-		<text><tspan font-family="Arial" >const accel 3</tspan></text>
+		<text><tspan font-family="Arial" >-0.25</tspan></text>
 	</g>
 </g>
 <g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
-	<path stroke='rgb(230, 159,   0)'  d='M516.2,88.7 L558.4,88.7 M55.3,422.4 L575.0,422.1  '/></g>
+	<path stroke='rgb(230, 159,   0)'  d='M516.2,88.7 L558.4,88.7 M55.3,422.4 L60.5,408.8 L65.7,395.1 L70.9,381.5 L76.1,367.9 L81.3,354.2
+		L86.5,340.6 L91.7,327.0 L96.9,313.3 L102.1,299.7 L107.3,286.1 L112.5,272.5 L117.7,258.8 L122.9,245.2
+		L128.1,231.6 L133.3,217.9 L138.5,204.3 L143.6,190.7 L148.8,177.0 L154.0,163.4 L159.2,149.8 L164.4,145.9
+		L169.6,145.9 L174.8,145.9 L180.0,145.9 L185.2,145.9 L190.4,145.9 L195.6,145.9 L200.8,145.9 L206.0,145.9
+		L211.2,145.9 L216.4,145.9 L221.6,145.9 L226.8,145.9 L232.0,145.9 L237.2,145.9 L242.4,145.9 L247.6,145.9
+		L252.8,145.9 L258.0,145.9 L263.2,145.9 L268.4,145.9 L273.6,145.9 L278.8,145.9 L284.0,145.9 L289.2,145.9
+		L294.4,145.9 L299.6,145.9 L304.8,145.9 L310.0,145.9 L315.2,145.9 L320.3,145.9 L325.5,145.9 L330.7,145.9
+		L335.9,145.9 L341.1,145.9 L346.3,145.9 L351.5,145.9 L356.7,145.9 L361.9,145.9 L367.1,145.9 L372.3,145.9
+		L377.5,145.9 L382.7,145.9 L387.9,145.9 L393.1,145.9 L398.3,145.9 L403.5,145.9 L408.7,145.9 L413.9,145.9
+		L419.1,145.9 L424.3,145.9 L429.5,145.9 L434.7,145.9 L439.9,145.9 L445.1,145.9 L450.3,145.9 L455.5,145.9
+		L460.7,145.9 L465.9,145.9 L471.1,145.9 L476.3,145.9 L481.5,145.9 L486.7,145.9 L491.8,145.9 L497.0,145.9
+		L502.2,145.9 L507.4,145.9 L512.6,145.9 L517.8,145.9 L523.0,145.9 L528.2,145.9 L533.4,145.9 L538.6,145.9
+		L543.8,145.9 L549.0,145.9 L554.2,145.9 L559.4,145.9 L564.6,145.9 L569.8,145.9 L575.0,145.9  '/></g>
 	</g>
-<g fill="none" color="#FFFFFF" stroke="rgb(230, 159,   0)" stroke-width="2.00" stroke-linecap="butt" stroke-linejoin="miter">
+	<g id="gnuplot_plot_5" ><title>0</title>
+<g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
+	<g transform="translate(507.9,110.6)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="end">
+		<text><tspan font-family="Arial" >0</tspan></text>
+	</g>
+</g>
+<g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
+	<path stroke='rgb(240, 228,  66)'  d='M516.2,106.7 L558.4,106.7 M55.3,422.4 L60.5,405.5 L65.7,388.6 L70.9,371.8 L76.1,354.9 L81.3,338.0
+		L86.5,321.1 L91.7,304.3 L96.9,287.4 L102.1,270.5 L107.3,253.6 L112.5,236.8 L117.7,219.9 L122.9,203.0
+		L128.1,186.1 L133.3,169.2 L138.5,152.4 L143.6,135.5 L148.8,118.6 L154.0,101.7 L159.2,84.9 L164.4,68.0
+		L169.6,51.1 L174.8,49.2 L180.0,49.2 L185.2,49.2 L190.4,49.2 L195.6,49.2 L200.8,49.2 L206.0,49.2
+		L211.2,49.2 L216.4,49.2 L221.6,49.2 L226.8,49.2 L232.0,49.2 L237.2,49.2 L242.4,49.2 L247.6,49.2
+		L252.8,49.2 L258.0,49.2 L263.2,49.2 L268.4,49.2 L273.6,49.2 L278.8,49.2 L284.0,49.2 L289.2,49.2
+		L294.4,49.2 L299.6,49.2 L304.8,49.2 L310.0,49.2 L315.2,49.2 L320.3,49.2 L325.5,49.2 L330.7,49.2
+		L335.9,49.2 L341.1,49.2 L346.3,49.2 L351.5,49.2 L356.7,49.2 L361.9,49.2 L367.1,49.2 L372.3,49.2
+		L377.5,49.2 L382.7,49.2 L387.9,49.2 L393.1,49.2 L398.3,49.2 L403.5,49.2 L408.7,49.2 L413.9,49.2
+		L419.1,49.2 L424.3,49.2 L429.5,49.2 L434.7,49.2 L439.9,49.2 L445.1,49.2 L450.3,49.2 L455.5,49.2
+		L460.7,49.2 L465.9,49.2 L471.1,49.2 L476.3,49.2 L481.5,49.2 L486.7,49.2 L491.8,49.2 L497.0,49.2
+		L502.2,49.2 L507.4,49.2 L512.6,49.2 L517.8,49.2 L523.0,49.2 L528.2,49.2 L533.4,49.2 L538.6,49.2
+		L543.8,49.2 L549.0,49.2 L554.2,49.2 L559.4,49.2 L564.6,49.2 L569.8,49.2 L575.0,49.2  '/></g>
+	</g>
+	<g id="gnuplot_plot_6" ><title>0.5</title>
+<g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
+	<g transform="translate(507.9,128.6)" stroke="none" fill="black" font-family="Arial" font-size="12.00"  text-anchor="end">
+		<text><tspan font-family="Arial" >0.5</tspan></text>
+	</g>
+</g>
+<g fill="none" color="black" stroke="currentColor" stroke-width="1.00" stroke-linecap="butt" stroke-linejoin="miter">
+	<path stroke='rgb(  0, 114, 178)'  d='M516.2,124.7 L558.4,124.7 M55.3,422.4 L60.5,399.0 L65.7,375.7 L70.9,352.3 L76.1,328.9 L81.3,305.6
+		L86.5,282.2 L91.7,258.8 L96.9,235.5 L102.1,212.1 L107.3,188.7 L112.5,165.3 L117.7,142.0 L122.9,118.6
+		L128.1,95.2 L133.3,71.9 L138.5,48.5 L143.6,25.1 L145.5,16.7  '/></g>
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+	<g id="gnuplot_plot_7" ><title>1</title>
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